United Airlines Holdings Inc. is requiring its passengers to complete a self-assessment health screening before flying, one of the furthest reaching efforts among carriers to keep the Covid-19 outbreak in check as travel resumes.

Customers will have to confirm they haven’t experienced coronavirus symptoms two weeks before flying and complete a checklist based on recommendations from the Cleveland Clinic, United said Wednesday.

The coronavirus pandemic has wreaked havoc on the airline industry by decimating travel demand since mid-March, with traffic through U.S. airports on Tuesday down more than 85% from a year earlier, according to government data. Now, as states and localities reopen for business, carriers are developing procedures to ensure that flying is safe.

United’s passengers will only receive boarding passes after acknowledging that they had reviewed the checklist. Travelers must affirm that they hadn’t been diagnosed with Covid-19 in the last 21 days, or experienced symptoms such as a cough or muscle pain in the previous two weeks. Passengers must wear face coverings on board.