Southwest Airlines passengers check in at New York's LaGuardia Airport. The Federal Aviation Administration on Wednesday issued an emergency order grounding Boeing 737 Max jets in the wake of the crash of an Ethiopian airliner. Richard Drew/AP hide caption
Last week, Southwest took more than 40 of some 750 aircraft out of service at four locations, spurring flight delays and cancellations. Ted S. Warren/AP hide caption
A Southwest plane taxis at the Seattle-Tacoma International Airport in Seattle. Ted S. Warren/AP hide caption
A crack is seen on a window of Southwest Airlines Flight 957 after an abrupt landing in Cleveland on Wednesday. Rachel Colby/AP hide caption
National Transportation Safety Board investigators examine damage to Southwest Airlines Flight 1380, which left one passenger dead and other injured on April 17. A passenger filed a lawsuit against the airline on Thursday. Handout/Getty Images hide caption
National Transportation Safety Board investigators examine damage to the engine of the Southwest Airlines plane that made an emergency landing at Philadelphia International Airport in Philadelphia on Tuesday. AP hide caption
Tammie Jo Shults kept a cool head as she navigated her stricken Southwest airliner to a safe emergency landing on Tuesday. Kevin Garber/AP hide caption
House Transportation and Infrastructure Committee ranking member Peter DeFazio, D-Ore., questions witnesses Tuesday during a hearing about about oversight of U.S. airline customer service. Chip Somodevilla/Getty Images hide caption
Passengers check in for flights with United Airlines at Chicago O'Hare International Airport. United, American and Delta now offer no-frills "basic economy" fares. Scott Olson/Getty Images hide caption
US Airways and American Airlines planes sit at the gates at Dallas/Fort Worth International Airport. LM Otero/AP hide caption
A Boeing 737 jetliner operated by Southwest awaits loading at the Little Rock, Ark., airport. Danny Johnston/AP hide caption
A frame grab provided by KSPR-TV shows Southwest Airlines Flight 4013 at Taney County Airport on Sunday. AP hide caption
This photo provided by Bobby Abtahi, shows what officials say was a plane where the nose gear collapsed during landing at New York's LaGuardia Airport on Monday. Bobby Abtahi/AP hide caption
Southwest Airlines jets at Sky Harbor International Airport in Phoenix. (October 2010 file photo.) Matt York/AP hide caption
This Southwest Airlines jet was forced to make an emergency landing after part of the fuselage ruptured on Friday. The hole was in the top of the plane, above a wing. Ross D. Franklin/AP hide caption