The U.S. Air Force readiness rate (percentage of available aircraft able to do their job) has traditionally been high compared to all other major air forces. But age and two decades of heavy use under wartime conditions has taken its toll. The workload for maintenance personnel is higher while budgets for maintenance are not keeping up. This has reduced readiness rates noticeably in the last few years, but completed to a decade ago the air force is doing rather well. Readiness rates or the percentage of your aircraft that are “mission-capable” varies by aircraft type and technology an aircraft is based on. Age is important but has less to do with it than you might think.
For example, the current rates for fighters are (rate from a decade ago in parenthesis, NA means not applicable because the aircraft was not in service back then);
F-15C, 71.5 (71) percent
F-15E, 71.2 (72.5) percent
F-16C, 70 (75.4) percent
F-22A, 51.7 (60.9) percent
A-10, 72.5 (70.5) percent
F-35A, 49.6 (NA) percent
The F-22 rate was higher a decade ago partly because it had overcome the problems of being a new aircraft. But the problem of high maintenance costs and lack of durability led to a slide from a high of 65 percent readiness four years ago to the current low rate. The many stealth features of this aircraft required special attention, and provided more items that can break. The F-35A was not yet in service a decade ago so this new stealth fighters is where the F-22 was back then. The F-35 was designed to overcome the readiness problems of the F-22.
For bombers, the rates are;
B-1B, 51.7 (43.8) percent
B-2A, 60.7 (54.9) percent
B-52H, 69.3 (74.6) percent
A decade ago the B-1B was cursed with additional components (especially hydraulics) that enabled it to fly fast and low. That capability was not used anymore, but the equipment is still there, and when any of it broke, the aircraft doesn't fly. The unused equipment was eventually removed, solving a lot of readiness problems. The B-2 has lots of stealth stuff but the air force has overcome many of its unique maintenance problems. Meanwhile, the ancient, but relatively simple, B-52 had the highest readiness rate and still is the cheapest to operate. But the B-52s were built in the 1960s and despite ongoing upgrades, age is catching up with the elderly but reliable heavy bomber. Heavy bombers, in general, have, because of smart bombs, been heavily used since 2001.
Transports also are relatively simple in terms of tech, and their readiness rates show this;
C-130E, NA (76.7) percent
C-130H, 68.3 (73.8) percent
C-130J, 76.7 (82.3) percent
C-17A, 82.6 (84.4) percent
C-5, 62.6 (52.7) percent
CV-22, 59.4 (54.3) percent
The lowest rates are either the result of age (the C-5) or lots of tech (the tilt-rotor CV-22).
Electronic warfare aircraft, despite all the complex electronics carried, are basically transports full of electronics and operators.
E-3, 69 (71.6) percent (AWACS)
E-8, 66.9 (81.1) percent (JSTARS)
MC-130H, 84.3 (70.6) percent
MC-130J, 79.3 (65.2) percent
Aerial tankers are transports, and quite elderly;
KC-10A, 79.7 (74.8) percent
KC-135R, 73 (81.1) percent
KC-135T, 73.8 (80.4) percent
The readiness rate for these old, and heavily used, aircraft does not reflect the large number (up to 20 percent) of aircraft that are pulled for major rebuilds. Thus the most decrepit tankers are not counted, keeping the readiness of aircraft in squadrons at a high rate. While the tankers are being replaced with a new model, that KC-46 aircraft is behind schedule because of quality control issues. Not a good sign because the new tanker is based on a proven and widely used Boeing 767 commercial transport.
UAVs are simple aircraft, and their high readiness rate reflects this;
MQ-1B, 73.7 (93) percent
MQ-9A, 90.2 (91.9) percent
RQ-4B, 73.7 (41.6) percent
One exception is the RQ-4 Global Hawk, which is a jet-propelled, trans-oceanic aircraft. It is a much more complex beast and has long had more maintenance problems. The air force is not happy with this and the RQ-4 is being phased out. The MQ-1 is officially retired and only a few remain. The MQ-9 is the main UAV, with about 250 in service. That’s more than many types of manned aircraft. UAVs are still seen as the future and by removing the crew, and all the gear needed to sustain them, aircraft become easier and cheaper to maintain.
Trainers are simple aircraft, and their readiness rates reflect this;
T-1A, 58.9 (79.7) percent
T-38A, 72.6 (80.4) percent
T-6A, 66 (80.3) percent
The air force only has one type of strategic (long distance, high altitude) recon aircraft. More than most jets, the U-2 is a powered glider. It is old (in design), simple and very reliable.
U-2, 76.9 (81.2) percent
The air force doesn't have many helicopters, and they are army models. The army designs its helicopters for easy maintenance and heavy use.
HH-60G, 70.7 (74.6) percent (search and rescue)
UH-1N, 83.6 (80.9) percent (transport)
New aircraft designs create often unique maintenance problems. For example, the F-22 aircraft proved more difficult to maintain than planned. Because of the time required to service the stealth features of the aircraft, only about 50 percent of them are available for service at any given time. Non-stealth fighters have a readiness rate of 70 percent. This is a persistent problem and largely has to do with the heavy maintenance required for the radar-absorbent skin on these aircraft.
Back in 2006, only about seven of the U.S. Air Force's 21 B-2 "Stealth" bombers were ready to go at any time. The air force is still trying to solve the problem. A decade ago it was hoped using a combination of robots, sprayers and quality control would double the readiness rate. This was essential because the B-2 was frequently getting called a "Hangar Queen" (an aircraft that spends too much time in the hangar for maintenance or repairs).
In 2013 the U.S. Air Force introduced the use of robots to reduce the maintenance efforts required to keep their B-2 bombers flying. The B-2 uses a stealth (anti-radar) system that depends a lot on a smooth outer skin. That, in turn, requires that the usual access panels and such on the B-2 must be covered with tape and special paste to make it all smooth. The F-22 uses a similar system. After every flight, a lot of this tape and paste has to be touched up, either because of the result of flying or because access panels had to be opened. All this takes a lot of time, being one of the main reasons the B-2 required 25 man-hours of maintenance for each hour in the air. Since most B-2 missions have been 30 or more hours each, well, do the math. The readiness rate of the B-2 fleet (currently 20 aircraft) has been as low as 35 percent, which was less than half the rate of most other aircraft. This means, that whenever there is a crisis that requires the attention of B-2s, there are not many of these bombers ready to fly.
The main base for B-2s is in Missouri, and over a thousand maintenance personnel were assigned to take care of 20 aircraft there. A team of four robots were installed, to liquid coat B-2s, thus cutting maintenance hours in half. But there were quality control problems with the liquid coating, often forcing maintenance crews to go back to tape and paste. Eventually, the quality control problems were solved, and, the readiness rate of B-2s went up to over 50 percent and is now 60 percent.
B-2s still require a special, climate-controlled hangar. There are some portable B-2 hangars, that can be flown to distant bases, thus keeping the bombers in the air less, and reducing the amount of maintenance needed. B-2 quality hangars were built at Guam, in the Pacific, and Diego Garcia in the Indian Ocean
These problems are still there, as are efforts to overcome. Stealth is still valuable but since 2001 it has rarely been critical. Now it is because the most likely opponent is China, which has modern air defense systems. The decade of effort to improve the readiness rate of the B-2 has paid off. Similar efforts are being applied to the slightly different stealth skin tech used in the F-22 and F-35.
There are two other issues that remain unresolved. One is the age of combat aircraft. The F-35 was late arriving in large numbers and the F-16s and F-15s they were to replace are still in service. As aircraft age, maintenance costs rise and the air force budget is not rising to deal with that. As a result readiness rates for these older aircraft have been falling during the last few years. At the same time, most of the aircraft have benefitted from tech upgrades. Not just new electronics but also components made of new materials. Despite all that, age and increasing maintenance costs eventually prevail in the form of lower readiness rates.