With its ability to refuel while airborne, the B-2 Spirit stealth bomber’s flight time is effectively limited only by the physical endurance of its pilots.

During the 37-hour mission to strike Iran’s nuclear facilities on June 22, that human limitation was pushed to the extreme.

“B-2 pilots can lie down to take a nap. However, they do so in the limited space behind the seats on a metal surface, which is not comfortable,” a spokesperson from the Whiteman Air Force Base in Missouri, where the stealth bombers are based, told RFE/RL.

Additionally, the air force spokesperson says, “the aircraft generates its own oxygen -- i.e., pulls it out of the atmosphere -- which results in almost no moisture in the aircraft, which in turn leads to pilots having to constantly hydrate while still experiencing issues such as dried and cracking skin.”

The B-2 was developed by the US during the Cold War as a nuclear-capable stealth bomber able to slip past the Soviet Union’s thousands of radar stations and avoid that country's formidable fleet of thousands more interceptor jets and surface-to-air missiles.

The B-2's “flying wing” design, as well as a top secret, radar-absorbing skin and other advanced technologies, gives the 52-meter-wide bomber the radar footprint equivalent to that of only a large bug. It was first flown in July 1989.

Lieutenant General Mark E. Weatherington is the Deputy Commander of the US Air Force Global Strike Command. He told RFE/RL that one of the most stressful aspects of a long-range mission such as the "Midnight Hammer" Iran strikes, is refueling behind a tanker aircraft, an operation required every six hours in the B-2. “Air refueling is absolutely crucial and if it’s dark, cloudy, turbulent etc., it can demand more focus,” he says.

Pilots have described finishing the delicate refueling operation, which requires around 30 minutes of intense focus, drenched in sweat.

And there is no shower or change of clothes for the pilots. B-2 bomber crews wear a harness, lifejacket and survival vest over their flight overalls, making a changing an overly complex procedure amid a combat mission.

Bare-Bones Crew

Refueling for the humans aboard the bomber is altogether less intense.

The B-2 is equipped with a microwave, and pilots take along food of their choice.

“We work with the pilots to offer suggestions for what to eat and when to eat, but each individual really brings what they want,” Weatherington says, adding, “hydration is crucial for such a long sortie.”

The B-2 was configured to seat a crew of up to three, but is flown by just two pilots, one of whom doubles as a mission commander.

That bare-bones crew is in part to keep costs down. Highly trained humans are one of the priciest aspects of advanced weapons systems and the B-2 has been dogged by criticism over its expense since inception. Each B-2 costs around $2 billion and 21 have been built.

Sleep Training

One result of flying with such a small crew is that pilots have little time to rest.

Weatherington says B-2 pilots picked for a combat mission spend several days working with an “aerospace physiologist” to align their sleeping pattern with the timetable of their upcoming mission. But he says, "how much and how well they sleep varies by individual."

Sleep training may have been introduced for B-2 pilots in the wake of the Kosovo War, when American airmen reported being so adrenalized amid the tension of combat that they became exhausted, yet unable to sleep even during long sorties.

B-2 pilots on previous combat missions have used amphetamine pills to stay alert.

After multiple refuelings, and intermittent rest on the secret flight to Iran, the most intense moment for the pilots would have been the strikes themselves, according to Weatherington.

"Executing the mission in the target area is likely the most stressful in this case," he says.

With seven B-2s dropping 14 massive bunker-busting bombs on a country that has previously shot down unmanned American aircraft, "operating almost independently in the target area but synchronized to achieve the results, it becomes a demanding mission," Weatherington adds.