Ahead of the summer travel season , airlines in the United States usually compete to sell tickets and fill seats .
But the airlines that operate the grounded Boeing 737 Max planes have a new problem : there are not enough seats to meet the demand .
The revenue is right in front of them . They can see it , but they can ' t meet it , said Mike Trevino .
He is an airline industry expert and spokesman for Southwest Airlines Pilots Association .
The grounding of Boeing ' s 737 Max came after two deadly crashes in five months .
Southwest Airlines is the world ' s largest 737 Max operator . The company has 34 of the planes .
American Airlines operates the second - most , with 24. These planes have been removed from use until at least August .
The grounding of the planes has led Southwest to cancel 160 of its 4 , 200 daily flights between June 8 and August 5.
American Airlines will cancel 115 daily flights , or 1.5 percent of its total summer flights .
Southwest only flies Boeing 737 s . It had estimated $ 150 million in lost revenue between February 20 and March 31 -- mostly because of MAX cancellations .
So far , airlines have said it is too early to estimate the cost of the Max grounding beyond the first three months .
However , continuous cancellations show that most airlines do not expect a fast return of the MAX model .
The 737 Max was grounded worldwide in March following a deadly Ethiopian Airlines crash .
It came five months after a Lion Air crash in Indonesia . All on board both planes died .
Boeing is under pressure to provide additional software .
Experts are examining the original software as a possible reason for the crashes .
Boeing must prove to worldwide regulators that the plane is safe to fly . That process may take more than 90 days .
Planes in the United States are usually mostly full during the months of June , July and August .
The U . S . Bureau of Transportation Statistics says this is when airlines earn the most money for each seat .
Lowering the number of seats could mean more costly summer prices .
United Airlines operates only 14 Max planes and has mostly avoided cancellations .
Instead , it has been more of its larger Boeing 777 or 787 airplanes .
However , the airline ' s president warned last week that the move has been very costly and that it could not continue doing so forever .
Although the MAX 737 makes up just 5 percent of Southwest planes and even less for other airlines , the problem may only get worse .
That is because Southwest , American and United all were expecting deliveries of new Max planes soon .
Southwest was expecting 41 in 2019 , while American was expecting 16 and United was expecting 14.
I ' m Ashley Thompson .