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 737s. 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.