The budget cuts known as sequestration are forcing the United States to ground hundreds of its warplanes, at a time when they are likely to be called upon in the event of a conflict with North Korea.

According to internal documents obtained by Air Force Times, an independent newspaper covering the service, the spending cuts that have gone into effect March 1 will result in 44,000 fewer flying hours until September, when the government’s fiscal year 2013 ends.

The newspaper cited a memo by Maj. Gen. Charles Lyon, director of operations for Air Combat Command, saying the Air Force’s budget for flying hours was reduced by $591 million for the remainder of the fiscal year, making it impossible to keep all squadrons ready for combat.

A request for comment from the U.S. Air Force on Tuesday morning was not answered immediately.

Seventeen Air Force squadrons will stand down on Tuesday, including the stealthy, advanced F-22 Raptor fighters from Langley Air Force Base in Virginia that were recently deployed to South Korea in a show of force. Other frontline planes grounded include part of the fleet of B-1, B-2 and B-52 heavy bombers that would form a fundamental part of any U.S. plan for war with North Korea.

Also grounded are the Thunderbirds, the Air Force’s aerobatic team, which will not perform at air shows this summer.

Air Force officials already told Congress that the sequester would reduce flying hours by 18 percent over the fiscal year and that combat readiness would drop to “sub-optimal levels.”

The Air Force units based in South Korea, closest to the theater of any future action against North Korea, are not affected. However, three important units flying the F-15 and F-16 in Japan, which would likely have been used in the event of conflict, have been reduced to “basic mission capable levels,” meaning they cannot operate at the fullest extent of their capabilities.

The planes affected by the sequester grounding include some of the following:

A-10 Thunderbolt aircraft being maintained
Twelve A-10 Thunderbolts have arrived in Estonia as part of a mission to protect European skies from Russian aggression. Pictured: An A-10 Thunderbolt II at Nellis Air Force Base in November 2011. U.S. Air Force/Tech Sgt. Michael R. Holzworth
B-1B Lancer
A B-1B Lancer flies Feb 26, 2011, above Iraq, in support of Operation New Dawn. (U.S. Air Force photo/Master Sgt. Adrian Cadiz)
B-2A Spirit
A B-2 Spirit flies June 4, 2011, above Ellsworth Air Force Base, S.D., during the 2011 Dakota Thunder air show. (U.S. Air Force photo/Tech. Sgt. Nathan Gallahan)
B-52H Stratofortress
A B-52H long-range bomber flies over the ocean. (U.S. Air Force photo/Staff Sgt. Kamaile O. Long)
F-15E Strike Eagle
An F-15E Strike Eagle soars over the runway Aug. 27, 2011, at Offutt Air Force Base, Neb., during the 2011 Defenders of Freedom Open House and Air Show. The F-15E is a dual-role fighter that can perform air-to-air and air-to-ground missions. (U.S. Air Force photo/Josh Plueger)
F-22A Raptor
A pair of F-22 Raptors pulls away and flies behind a KC-135 Stratotanker after receiving fuel off of the East Coast on July 10, 2012. The 1st Fighter Wing at Joint Base Langley-Eustis, Va., received their first two Raptors in January 2005 and the wing’s 27th Fighter Squadron was designated as fully operational in December 2005. The Raptors belong to the 27th FS and the KC-135 belongs to the 756th Air Refueling Squadron at Joint Base Andrews Naval Air Facility, Md. (U.S. Air Force photo/Master Sgt. Jeremy Lock)
F-16 Fighting Falcons with the Thunderbirds, the U.S. Air Force aerial demonstration team, perform during the 2011 Legacy of Liberty Air Show on Oct. 8, 2011, at Holloman Air Force Base, N.M. (U.S. Air Force photo/Senior Airman DeAndre Curtiss)