The consultancy, which will work with BA on brand strategy, joins M&C Saatchi, Interbrand and ZenithOptimedia in BA's line-up of agencies.
Leslie Butterfield, a managing partner at Ingram, will run the account and work with BA on deciding how the brand should evolve. Butterfield has worked with airlines such as Emirates, bmi, and British Caledonian in the past.
Ingram will work closely with Jill McDonald, BA's general manager, global marketing and inflight business, on brand positioning across BA's global services.
McDonald said: "British Airways is proud of its brand heritage. The travel industry is constantly evolving, so our task is to ensure that we remain ahead of the game."
The BA win comes a fortnight after Carol Fisher, one of Ingram's founding managing partners, announced that she was leaving the consultancy. She is taking time out to consider her options.