Initial reports claimed a cabin fire forced the US Navy E-6B Mercury to land at Tulsa International Airport at about 3 p.m. local time, but the US Navy contradicted those stories, saying a faulty water separator had sent fumes through the aircraft and driven the crew to land suddenly, and there had been no fire or fire alarm.

The crew deployed emergency slides to exit the plane once on the ground, The Aviationist reported, and at least one crew member could be seen covering their face, perhaps to keep from inhaling the fumes, as they exited the aircraft. According to Military.com, the E-6B carries a crew of 22.

The official Twitter account of Tulsa airports tweeted a statement about the incident, noting, “At 3:09 PM a military aircraft made an emergency landing at TUL without incident. In an abundance of caution, the crew elected to deplane the aircraft on a nearby taxiway. None of the 22 passengers on board were injured. The airport remained open with flights landing on the crosswind runway until the main runway opened a short time later. Flight operations have returned to normal.”

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US Upgrade of Nuclear Forces to Cost More Than Expected

The Navy’s Mercury aircraft are tasked with acting as communications transit hubs and potential moving command centers in the event of a nuclear war. An Aviationist report on the Mercury says it is able “to communicate on virtually every radio frequency band, on commercial satellites and on the Internet, using also a secure VOIP [voice over internet protocol] system. This aircraft usually operates flying orbits/circles while trailing their antennas.” The planes would keep the US president, secretary of defense and other decision makers in contact with America’s nuclear-armed aircraft and submarines as well as its missile stockpiles.

These Doomsday planes are operated out of Tinker Air Force Base in Oklahoma as part of the Navy’s Strategic Communications Wing One, which supports its “Take Charge and Move Out” system to provide survivable communications during a nuclear conflict. An E-6B was damaged at the base last month to the tune of millions of dollars when its tail clipped a part of a hangar there.