United Airlines is considering shutting three of its four international flight attendant headquarters in October as the ongoing health crisis continues to deal a heavy blow on global aviation operations and demand. 

According to a company memo seen by CNBC, the Chicago-based carrier will close facilities in Japan's Narita airport, Frankfurt and Hong Kong. United Airlines disclosed around 840 flight attendants are assigned in the three locations that are shutting down.

Some of the crew will be eligible to transfer to bases in the US as of the carrier's October flight timeline, assuming they are qualified to work in the United States.

Airline companies are burning a huge amount of money as the pandemic continues to ravage the aviation market, with international flights taking the most of the beating from government-mandated travel bans and falling demand. The Chicago-based airline's London hub will not be closed down, John Slater, United's director of inflight services disclosed in a memo to personnel on Friday.

Having been granted $5 billion in bailout by the CARES Act, United Airlines is prohibited from cutting its workforce until October 1. The three international crew locations are scheduled to be closed at the earliest possible time allowed under the terms of CARES policies and the decision was carried out with only the 90-day notification period needed in the flight attendant agreement.

In the internal memo, Slater pointed out that United's move was truly a "very difficult decision to make... in the current and future environment, we simply aren't able to sustain an Inflight Base at these locations," as reported by Leslie Josephs of CNBC.

United Airline's chapter of the Association of Flight Attendants, which represents the carrier's approximately 24,000 cabin crew members called the decision "a shock" that will "create tremendous uncertainty" for all of them.

The union stated that United Airline's decision not to provide transfer opportunities for its London base was a serious concern and that it would create a dispute over the issue.

In a recent official communication, the union had called on US-based flight attendants to show unanimity with their airline colleagues deployed in foreign locations after some suggested that they may be the first workers to be given the pink slip.

Meanwhile, airline companies, which are poised to gain from the reopening of the US economy, rallied late Friday following a better-than-predicted employment data. American Airlines was up over 15 percent, while United Airlines and Delta climbed 13 percent and 9 percent, respectively.