Almost a dozen Am Law 100 firms have landed lead advisory roles on the proposed $11 billion merger of American Airlines parent AMR and US Airways Group—a Valentine’s Day deal that could create the world’s largest airline.

Thursday’s announcement that the two companies have agreed to merge follows months of negotiations that began when US Airways started circling its insolvent rival last year. Should the deal secure the required regulatory, shareholder, and creditor approvals, it would cap more than a decade of consolidation in the U.S. commercial aviation industry.

The AMR bankruptcy, which began when the carrier glided into Chapter 11 in November 2011, has already generated millions in legal fees for a variety of firms. AMR alone is paying at least 20 law firms—including the now-defunct Dewey & LeBoeuf—and navigating the looming regulatory approval process is likely to fatten at least some of those firms’ coffers even more.

Weil, Gotshal & Manges is serving as lead bankruptcy and deal counsel to longtime client AMR through corporate and M&A partners Thomas Roberts and Glenn West—the managing partner of the firm’s Dallas office—and business finance and restructuring partners Stephen Karotkin and Alfredo Perez.

West and Roberts both split their time between New York and Dallas and also sit on Weil’s management committee. The firm has a longtime client relationship with Fort Worth–based AMR, and Roberts was named an American Lawyer Dealmaker of the Year in 2001 for advising the company on its $500 million purchase of the assets of bankrupt Trans World Airlines. (Roberts, who chaired Weil’s corporate group from 2000 to 2011, was also named an American Lawyer Dealmaker of the Year in 2012 for his work advising Kinder Morgan on its $38 billion acquisition of El Paso Corporation.)

Another key lawyer working with AMR is Mary Korby. A former corporate partner at Weil, Korby left the firm on January 1 after reaching its mandatory retirement age and joined K&L Gates in Dallas, according to sibling publication Texas Lawyer. Korby has continued to advise AMR at K&L Gates, according to those close to the negotiations.

Other Weil lawyers working on the mega-merger include corporate partners Corey Chivers and Ted Waksman, bankruptcy partner Stephen Youngman, tax partner Stuart Goldring, executive compensation and employee benefits partner Michael Kam, litigation partner Richard Rothman, corporate governance partner Holly Gregory, tax counsel Max Goodman, restructuring counsel Michele Meises, and associates Jennifer Britz, Barbra Broudy, Pablo Falabella, David Gail, Dilen Kumar, Eric Schecter, Sunny Singh (he of Lehman Brothers bankruptcy billing fame), Ben Solaimani, Audrey Susanin, Ryan Taylor, Brett Thorstad, and Gavin Westerman.

Bankruptcy court records show that Weil has been paid more than $38.9 million by AMR since the start of the company’s Chapter 11 case through December 31. The Am Law Daily reported last year that Weil received $9.9 million in fees from AMR in the year prior to its Chapter 11 filing, including a $2.2 million retainer to advise on the airline’s restructuring.

As a matter of comparison, Kirkland & Ellis once reaped more than $100 million in fees for its work handling the three-year bankruptcy of United Airlines that ended in 2006. Davis Polk & Wardwell billed for more than $40 million in fees as a result of its role advising Delta Air Lines on its Chapter 11 proceedings that concluded in 2007.

Other Am Law 100 firms have also reaped the benefits from AMR’s 14 months in bankruptcy court.

Paul Hastings, which is serving as special labor and antitrust counsel to AMR, has been paid nearly $14.8 million by the debtor through December 31. Labor and employment senior counsel John "Jack" Gallagher, appellate practice cochair and employment litigation partner Neal Mollen, litigation and compliance partner Scott Flicker, and labor and employment partners Jon Geier and Todd Duffield are advising AMR along with antitrust partner M.J. Moltenbrey and associate Timothy Longman.

Moltenbrey joined Paul Hastings last May from Dewey, a firm she joined in March 2011 following the collapse of her previous firm, Howrey. AMR retained Dewey as its special litigation counsel last March, and bankruptcy court records show the bankrupt firm was paid $3.65 million for its services after filing its final fee application in late August. (Cooley, a firm that picked up several other Dewey defectors, has been paid more than $1.4 million by AMR.)

Jones Day is also serving as U.S. antitrust cocounsel to AMR on its proposed tie-up with US Airways. Antitrust partners Joe Sims and J. Bruce McDonald are leading a team from the firm working on the matter.

Debevoise & Plimpton is serving as special aircraft counsel to AMR through aviation practice chair John Curry III, restructuring cochair Richard Hahn, corporate and restructuring partners Jasmine Ball and My Chi To, tax partners Vadim Mahmoudov and Robert Staffaroni, and litigation and bankruptcy partner Michael Wiles. In 2011, Curry led a Debevoise team advising AMR on its $38 billion purchase of 460 aircraft from Airbus and Boeing.

Bankruptcy court records show that AMR has paid Debevoise nearly $21.1 million for its services through December 31. Another firm with ties to Weil, Texas litigation boutique Yetter Coleman, has received nearly $2.7 million through that same time period in its role as special litigation counsel to the debtor. Yetter Coleman founding partner Gregory Coleman—the Lone Star state’s first solicitor general and the former head of the national appellate practice at Weil—died tragically in a plane crash in 2010.

Other top AMR billers during the company’s Chapter 11 layover include special benefits counsel the Groom Law Group ($4 million), special litigation counsel Kelly Hart & Hallman ($1.9 million), special labor and employment counsel Morgan, Lewis & Bockius ($1.7 million), special union counsel Sheppard, Mullin, Richter & Hampton ($1.4 million), corporate counsel Winstead ($1 million), special labor and employment counsel Ford & Harrison ($776,000), special counsel Haynes and Boone ($759,000) special litigation counsel Harris, Finley & Bogle ($673,000), and special IP counsel Brinks Hofer Gilson & Lione ($669,000).

Gary Kennedy has served as AMR’s general counsel and chief compliance officer since 2003. Kennedy is leading an in-house team working on the merger that includes corporate secretary Kenneth Wimberly and associate general counsel Tim Skipworth, Kathryn Koorenny, and David Allen. William Ris Jr. serves as senior vice president of government affairs for AMR.

Sources close to the matter, who requested anonymity in order to speak freely about the historic transaction, say that AMR had to stabilize its own operations before moving forward with the merger with US Airways. And because AMR is still mired in bankruptcy, the complex deal must be approved not only by U.S. antitrust regulators, but also by creditors in the airline’s Chapter 11 case.

Skadden, Arps, Slate, Meagher & Flom corporate restructuring partners John "Jack" Butler Jr., and Jay Goffman are leading a team from the firm advising AMR’s official unsecured creditors committee. Butler and Goffman are veterans of airline bankruptcies, and Skadden advised America West Airlines on its 2005 acquisition of US Airways out of bankruptcy, the second time in three years the latter was forced into Chapter 11.

Also working on the current matter for Skadden are restructuring partners John Lyons, Ron Meisler, and Felicia Perlman, M&A partners Eric Cochran and Sean Doyle, antitrust partner James Keyte, banking partner Sarah Ward, executive compensation and benefits partner Neil Leff, IP and technology partner Jose Esteves, labor and employment partner John Furfaro, litigation partner Albert Hogan III, real estate partner Paul Huff Jr., tax partner David Polster, and environmental practice head Don Frost Jr.

Court records show that Skadden has been paid more than $12.7 million for its services in AMR’s Chapter 11 case through December 31. New York bankruptcy boutique Togut, Segal & Segal, which is serving as cocounsel to the creditors committee, has been paid more than $1.1 million during that same period. (Togut is also serving as lead debtor’s counsel in Dewey’s Chapter 11 case.)

As currently structured, terms of the proposed merger deal call for AMR’s creditors and other stakeholders (including unions representing pilots and other airline employees) to own 72 percent of the combined company, which will operate under the American Airlines brand. US Airways shareholders, who must also still approve the deal, will own the remaining 28 percent of the combined airline. Because he is overseeing AMR’s Chapter 11 case in Manhattan, U.S. Bankruptcy Judge Sean Lane—appointed to the bench in 2010—must approve any final transaction.

The Am Law Daily reported last year that Latham & Watkins had landed the lead role advising US Airways on a potential bid for AMR. Over the course of the ensuing 12 months, the Tempe, Arizona–based airline’s lawyers and financial advisers began putting in place the building blocks for a merger, including striking a key agreement last April with AMR’s union leaders to secure their support for the deal.

Latham corporate partners Peter Kerman and Anthony Richmond and bankruptcy partner D.J. "Jan" Baker—who joined the firm from Skadden in 2009—have taken the lead advising US Airways in connection with its pursuit of AMR. Rounding out the firm’s team on the matter are corporate partners Josh Dubofsky and Gregory Rodgers, bankruptcy partners Paul Harner and Robert Klyman, tax partner Kirt Switzer, employee benefits partners James Metz and Robin Struve, finance partner Kevin Fingeret and Graeme Smyth, real estate partner Kim Boras, environmental partner Joel Mack, corporate counsel Karen Eberle, environmental counsel David Langer, and associates Anitha Anne, Beth Beaury, Tiffany Campion, Michelle Carpenter, Daniel Costa, Gabriel Edelson, Lauren Follett, Jude Gorman, Milad Hassani, Timothy Ho, Sabina Jacobs, Abtin Jalali, Corinna Liebowitz, Catherine Martin, David McElhoe, Lauren Murphey, Saied Pinto, Douglas Shaw, Aaron Singer, Shi Su, and Zhao Yang.

Paul Galleberg, vice president of legal affairs at US Airways, is a former Latham partner who joined the airline in 2011. Galleberg is leading a group of in-house attorneys working on the merger that includes head of litigation and labor legal affairs Paul Jones, antitrust expert and vice president of legal and government affairs Howard Kass, and executive vice president of corporate and government affairs Stephen Johnson, a key legal adviser who joined the airline in 2009 from Phoenix-based private equity firm Indigo Partners. Also advising on the merger with AMR are US Airways associate general counsel Alan Davis and Mark Burgoz, and assistant general counsel Ann Halton.

Dechert antitrust partner Paul Denis is also advising US Airways, along with Charles “Rick” Rule, head of the antitrust group at Cadwalader, Wickersham & Taft. Rule has been a longtime legal adviser to US Airways, having represented the company on a series of scuttled tie-up talks with United Airlines and a failed attempt to merge with Delta in 2007. (Rule was chair of the antitrust practice at Fried, Frank, Harris, Shriver & Jacobson at the time—he left for Cadwalader in April 2007.)

O’Melveny & Myers labor and employment partner Robert Siegel is also advising US Airways, which kept its current name after being bought by America West in 2005.

Overcoming regulatory hurdles will be a key factor in achieving any final deal with AMR, and other Am Law 100 firms like Duane Morris are advising US Airways on regulatory issues at the state level, according to sibling publication The Legal Intelligencer.

Shearman & Sterling M&A partners Peter Lyons and David Connolly, bankruptcy partner Douglas Bartner, litigation partner Alan Goudiss, and associate Meghan Moore are leading a team from the firm representing Barclays, which is serving as financial adviser to US Airways on the proposed merger with AMR.

Jenner & Block is representing a committee of retired AMR employees in the airline’s Chapter 11 case. Court filings show that AMR has paid Jenner $547,000 through December 31, as well as another $421,000 during that same period to Milbank, Tweed, Hadley & McCloy, which is advising an ad hoc group of bondholders. A support and settlement agreement filed by AMR with the SEC on Thursday shows that White & Case and Kramer Levin Naftalis & Frankel are advising other debt holders.

Robert Keach, cochair of the business reorganization and insolvency practice at Portland, Maine–based Bernstein, Shur, Sawyer & Nelson, was appointed as fee examiner in AMR’s bankruptcy case last June. Court records show the firm has been paid $756,000 by AMR through December 31.

If the merger is completed, the combined entity will employ 100,000 people and run 6,700 daily flights on 900 aircraft around the world. In 2010, five large firms grabbed lead roles advising on the combination between United Airlines and Continental Airlines, according to our previous reports.