Southwest Airlines and American Airlines have lost hundreds of millions of dollars in revenue and have taken big hits to their capacity since the troubled Boeing 737 MAX groundings on March 13.

That’s the grim finding in a new report out on Tuesday from airline data behemoth OAG.  

According to OAG’s calculations of planned capacity at affected airlines with the MAX still flying versus the actual capacity since the MAX groundings, the capacity losses among United States-based carriers with 3 million seats at Southwest Airlines, which has 34 MAX planes, the largest number of MAXs of any airline in the world.

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American Airlines, which has 24 Boeing MAX planes, per OAG calculations, has seen its capacity drop by 2.2 million seats since the MAX grounding.

Altogether across North America, OAG said more than 11 million seats have been dropped from sales in recent months. That's compared to the schedules affected North American carriers had on file in February of this year before two fatal crashes resulted in the grounding of all MAX planes worldwide.

And what about the revenue lost to carriers because of all this lost seat capacity?

Per OAG data crunching, the cost to U.S. airlines could run to $4 billion if the MAX somehow manages to return to service by November — a deadline many observers now consider a remote possibility at best.

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