Southwest Airlines Co., a discounter that flies mostly in the U.S., is the world’s largest carrier—for now.

The ranking is based on the number of seats flown this week, as compiled by aviation data provider OAG. Southwest moved to the top spot as its larger rivals nearly abandoned international routes after governments worldwide restricted travel to stem the spread of the new coronavirus. U.S. domestic service, in which Southwest is a bigger player, hasn’t been cut as sharply.

U.S. airlines have reduced seats flown by more than 60% since Jan. 20, according to OAG. Carriers have slashed flying capacity, parked planes and taken other steps to cut costs as the number of U.S. passengers has plunged more than 95% from a year ago.

Southwest, which first moved into the top slot the week of April 6, is operating just over 3 million seats this week, followed by American Airlines Group Inc., with nearly 2.1 million, according to OAG. Delta Air Lines Inc. ranked fifth among global carriers, followed by United Airlines Holdings Inc. American last year was the world’s largest carrier based on miles flown by paying passengers.

OAG cautioned that the weekly data have been particularly volatile, filed by “airlines who are under tremendous pressure adjusting and working through schedule changes.”