ROME — The fiscal 2019 budget for the U.S. Air Force plans to grow the service from 55 to 58 combat squadrons over the next five years, while buying dozens of high-end aircraft and preparing to retire the B-1 and B-2 bomber fleets as the military retools for the high-end competition forseen by the Pentagon.

The National Defense Strategy, released in January, focused on the potential for great power competition between the U.S. and Russia or China. And in any such battle, the U.S. Air Force would play a critical role; hence, the service’s request for $156.3 billion for FY19, a 6.6 percent overall increase from the FY18 request.

In FY19, the Air Force is requesting 48 F-35A fighter jets, 15 KC-46A tankers and one more MC-130J aircraft. Ther service is also investing $2.3 billion in research and development in the B-21 Raider bomber, up from the $2 billion request in the yet-to-be-enacted FY18 budget.

The latter is notable, as the Air Force has formally announced it will be retiring the B-1 and B-2 bomber fleets once the B-21 — which will be dual-capable for both conventional and nuclear missions — starts to come online in the mid-2020s.

The budget request also calls for investing in new engines for the B-52 fleet to keep that aircraft going through 2050 — making it an almost 100-year-old design.

“If the force structure we have proposed is supported by the Congress, bases that have bombers now will have bombers in the future,” Air Force Secretary Heather Wilson said in a service release. “They will be B-52s and B-21s.”

The budget request also seeks to move forward with a new light-attack aircraft, likely either the Embraer-Sierra Nevada Corp. A-29 Super Tucano or the Textron AT-6, to provide a low-end capability.

Although that program seems at odds with the high-end challenge foreseen by the Defense Department, Susanna Blume of the Center for a New American Security believes it fits in nicely, as such an aircraft would remove the need to fly expensive, high-end aircraft for that mission.

Overall, the budget request calls for buying 258 F-35A fighters through the next five years. And in terms of space, the service is requesting $2 billion to fund five launches of the Evolved Expendable Launch Vehicle.

The service also seeks to increase funding for F-16 modernizations to speed upgrades with the active electronically scanned array antennas, radar warning systems and Link 16 systems.

Naval warfare reporter David B. Larter contributed to this report from Washington.