Delta Air Lines will charge employees on the company health plan $200 a month if they fail to get vaccinated against COVID-19, a policy the airline's top executive says is necessary because the average hospital stay for the virus costs the airline $40,000.

CEO Ed Bastian said that all employees who have been hospitalized for the virus in recent weeks were not fully vaccinated.

The airline said Wednesday that it also will stop extending pay protection to unvaccinated workers who contract COVID-19 on Sept. 30, and will require unvaccinated workers to be tested weekly beginning Sept. 12, although Delta will cover the cost. They will have to wear masks in all indoor company settings.

Delta stopped short of matching United Airlines, which will require employees to be vaccinated starting Sept. 27 or face termination. However, the $200 monthly surcharge, which starts in November, may have the same effect.

"This surcharge will be necessary to address the financial risk the decision to not vaccinate is creating for our company," Bastian said in a memo to employees.

Bastian said that 75% of Delta employees are vaccinated, up from 72% in mid-July. He said the aggressiveness of the leading strain of the virus "means we need to get many more of our people vaccinated, and as close to 100% as possible."

The Delta CEO referred to the COVID-19 mutation that originated in India by by its medical name, B.1.617.2, rather than the more common term, the delta variant.

New reported cases of COVID-19 in the U.S. now top 150,000 a day, the highest level since late January, although the rate of increase has slowed. Southwest, Spirit and Frontier have blamed the virus for a slowdown in customers booking flights, and U.S. air travel remains down more than 20% from pre-pandemic 2019.

Delta and United already require new hires to be vaccinated. Other major U.S. airlines, including American and Southwest, say they are encouraging employees to get vaccinated but have not required it.

Delta's requirement for weekly testing of unvaccinated employees will start Sept. 12, and the requirement that the unvaccinated wear masks indoors takes effect immediately.

A growing number of companies including Chevron Corp. and drugstore chain CVS announced they will require workers to get vaccinated after this week's decision by the Food and Drug Administration to give full approval instead of just emergency-use permission to the Pfizer vaccine.

The FDA's move could boost the U.S. vaccination rate, which fell from 3.4 million shots a day in April to about 500,000 a day in July. It has since climbed to about 850,000 a day as concern grows about a rising number of new infections caused by the delta variant.