WASHINGTON - U.S. airlines are stepping up their efforts to get the Biden administration to end COVID-19 pre-departure testing requirements for international air travel.

American Airlines Chief Executive Robert Isom said on Friday at a conference the testing requirements were "nonsensical" and were "depressing" leisure and business travel.

Airlines say many Americans are not traveling internationally because of concerns they will test positive and be stranded abroad. International U.S. air travel remains down about 14% from pre-pandemic levels.

Isom, who met with politicians in Washington on Thursday to discuss the issue, said 75% of countries American serves do not have testing requirements. The Centers for Disease Control and Prevention (CDC) requires travelers to test negative within one day before flights to the United States.

"We're really frustrated and this is something that is damaging not only U.S. travel but it just doesn't make sense," Isom said.

He noted testing rules do not apply to people crossing U.S. land borders and noted the Boston Red Sox baseball team in April flew to Toronto to play the Blue Jays - but rode a bus home to avoid the testing requirements.

White House Press Secretary Karine Jean-Pierre said on Wednesday the administration was "constantly evaluating our policy.... And any decision on pre-departure testing requirement would be made by our health and medical experts."

Delta Air Lines Chief Executive Ed Bastian told Reuters on Wednesday that dropping the requirements will boost travel. He said 44 of 50 countries Delta serves do not require testing.

"We know it will help induce and incent travelers to go abroad, bring more commerce in, more business in so hopefully they will get it done soon," Bastian said.

Airlines for America, an industry group representing major carriers, and U.S. Travel met with a deputy White House COVID-19 coordinator Tuesday, who gave no indication of when the Biden administration might rethink the requirement.