Russia’s attack on Ukraine is disrupting the air travel sector, causing no-fly areas and other restrictions.

The Ukraine’s airspace was closed just moments before Russia invaded it on Thursday morning. This prevented an exit point.

Wizz Air, a discount carrier, stated Friday that it is trying to rescue crews trapped in Ukraine.

Christie Rawlings, spokeswoman for the organization stated in an email that “we are still working hard” to help them get out as soon as possible. “We keep in touch with each member of the crew to confirm that they were all able get out via ground transportation. Most of the employees who are based in Ukraine are Ukrainian citizens.”

KLM Royal Dutch Airlines, Lufthansa Group and others had previously stopped flights to Ukraine.

CNBC was informed Friday by KLM that some flights to Russia were being canceled so crews don’t need to spend the night there.

Aircraft were not allowed to fly into Moldova or parts of Eastern Russia. Since the Russian missile that hit eastern Russia in 2014 killed Malaysia Airlines Flight MH17, many airlines avoided this region.

British officials tried to stop Russian Airlines Aeroflot’s landing in the country. Russia responded by banning British aircraft from Russia’s airspace.

In the days leading up to the invasion, some airlines were already rerouting their planes around potential conflict zones.

Bruce Chan, Stifel’s logistics analyst, stated that “any divertions aircraft must make in order to get around the no fly zone are going to increase fuel costs.”

The higher costs could be a result of an increase in fuel prices, which is already a problem for airlines.

United Parcel ServiceThis week I started to fly a southerly route through Ukraine.

The airline sent a message on February 21 to pilots, saying that while the alternate route may take longer to fly, it is still a feasible alternative and will continue providing safe and efficient operations. “We will monitor the situation closely and send you any additional updates as soon as we have them.”

CNBC reported that international carriers inquired about ground support and fuel availability at Anchorage Airport in Alaska. Anchorage Airport is an important cargo airport. These questions indicate that airlines have begun to develop contingency plans in case more Russian airspace is closed.

Delta Air LinesAeroflot suspended their codeshare agreement on Friday, which had allowed them to each book flights on the other’s behalf.