United Airlines (UAL) is set to terminate employees who refuse to get the coronavirus vaccine, under a policy it first established in August.

The Chicago-based company has a total of 593 staff members who have not yet been jabbed, and have not applied for an exemption on religious or medical grounds.

They now face being fired by the airline for failing to comply with its vaccination rules, however, they will be given a final chance to fall into line, United said.

United required its 67,000 US staff members to provide proof of vaccination by 27 September.

Employees were given an added incentive of receiving an extra day’s pay if they got their full vaccination dose before 20 September.

Read more: Morgan Stanley wants proof employees have been vaccinated

Some 2,000 employees have requested an exemption to the policy, accounting for less than 3% of the airline's workforce.

At the time of that announcement, 90% of its pilots and 80% of its flight attendants had already been vaccinated.

"Our rationale for requiring the vaccine for all United's US-based employees was simple – to keep our people safe – and the truth is this: everyone is safer when everyone is vaccinated, and vaccine requirements work," chief executive Scott Kirby and president Brett Hart said on Tuesday.

"This was an incredibly difficult decision, but keeping our team safe has always been our first priority,” they said in a memo to employees.

The company confirmed that it would follow the rules outlined in union agreements on the dismissals. But the overall process could take weeks or months to complete.

Read more: Airline stocks rise on reports UK set to relax travel rules

A company spokesperson also added that United is looking to hire about 25,000 people during the next few years, and that vaccination will be a condition of employment for all new hires.

Students at its pilot training school will also be required to get vaccinated.

United received 700 applications for around 400 job postings last month at a Denver career fair. Similarly, it has received more than 20,000 applications for 2,000 open positions for flight attendants.

United is one of a number of airlines that has made vaccination mandatory for its staff. Delta Airlines (DAL) recently announced plans to put a $200 (￡148) surcharge on the health plan of unvaccinated employees starting on 1 November.

Watch: Should I book a holiday in 2021?