American has finished adding seats to its Boeing 737 fleet — and the Airbus A321s are just a step behind

The ironically named Project Oasis is one step closer to completion.

American Airlines has finished the "Project Oasis" retrofit of its Boeing 737-800 fleet, airline president Robert Isom said on Thursday, adding that he expects a similar retrofit to be completed on the airline's Airbus A321 fleet by the end of the year.

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The Oasis project harmonizes disparate cabins across American's 737 and A321 fleets. The 737s gain 12 seats, bringing them up to 172 — the same amount as on the airline's 737 Max — and the A321s go from as few as 181 seats to 190.

Despite the name, passengers have been mostly displeased with the changes, which — by the nature of adding seats — means less room (or padding) for the existing seats. American previously updated its changes to the first-class cabin of the 737, following customer complaints.

Although American briefly paused the retrofit in 2019 to avoid cancelations stemming from the 737 Max grounding, it resumed with gusto in late-2020, taking advantage of pandemic-related travel lulls to accelerate the work.

"We sped both of those projects up during COVID because, as you know, we didn’t need all those planes," Chief financial officer Derek Kerr said on Thursday during a Bernstein investor event. "So we were able to put more planes in there and bring those projects much faster to the front."

It was not clear exactly when the project was completed on the 737s. The airline said in October, 2020 that it expected to finish the work by this March, up from the previous goal of April.

The A321 timeline, however, has moved up significantly. Kerr said last year that the company was aiming to complete the retrofit on those aircraft by spring 2022.

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The densification, while not a passenger favorite, has been viewed by airline executives and investors as a cost-saving measure, thanks to the ability to sell more seats, as well as the simplification created by standardizing the fleets.

American now has just four aircraft types across its mainline fleet, with — once the A321 updates are done — uniformed seat maps across each type.