The Boeing 737 Max grounding will cost American and Southwest Airlines at least $1 billion combined.
Southwest, the largest Max customer, said the grounding cost $435 million through the end of September, while American Airlines estimates a loss of $540 million.
All Max jets have been idle since a worldwide grounding began in March this year.
American said it cancelled nearly 10,000 flights due to the grounding in the third quarter alone.
Like many airlines Southwest is still negotiating with Boeing over compensation.
United Airlines which has 14 Max jets, has not publicly disclosed how much it has lost over the Max inactivity.
Boeing has set aside $5 billion to cover compensation for all Max airline customers but that is looking increasingly inadequate as the grounding drags on.
In addition to airline compensation claims pilot unions have filed lawsuits hoping to recover millions for lost wages due to the grounding.
There was yet more bad news for Boeing as the final crash investigation report of the Lion Air crash was published.
It blamed a complex chain of events for the crash including design flaws, and parts that had not been properly tested.
The FAA was also criticized for lax oversight.
