The U.S. Air Force will have to curtail its orders for Lockheed Martin Corp’s F-35 fighter jet, restructure a $52 billion tanker contract with Boeing Co and reduce its flying hours by 18 percent if lawmakers do not avert impending across-the-board spending cuts, the service told Congress on Wednesday.

The Air Force, in a draft presentation to Congress, said it faced shortfalls of $1.8 billion in war funding and $12.4 billion overall if Congress does not forestall the cuts, known as sequestration, which are due to take effect on March 1.

The impact of sequestration would be exacerbated, the Air Force said, if Congress did not pass a budget for the current fiscal year and stuck with the stop-gap spending measure currently in place, known as a “continuing resolution,” or CR.

“Without substantial reprogramming flexibility, a year-long CR and sequestration disrupts modernization programs” and means a delay in getting weapons into the hands of troops, according to the presentation, a copy of which was obtained by Reuters.

It cited several examples, including expected reductions in the number of F-35 purchases, the need to renegotiate a big contract with Boeing for new refueling planes, and a delay in a new version of the MQ-9 Reaper drone built by privately held General Atomics.

The stop-gap spending measure prohibits any new programs from starting, and limits spending to what it was in the previous fiscal year’s budget, hindering the ramping up of planned spending for new programs.

The Air Force said acquisitions of several weapons systems built by Lockheed Martin - new missile warning satellites, C-130J transport planes and the F-35 Joint Strike Fighter - were already being delayed.

It said it also faced the possibility of a short-term furlough of 180,000 civilian contractors, an unprecedented action that would delay testing of new weapons systems, which in turn would raise program costs and delay programs.

The service said more than 30 weapons systems would face reduced maintenance, affecting nearly all fighter jets, transport planes and bombers in the Air Force fleet.