Iran in 2015 fitted one of its old, American-made RH-53D helicopters—nose number “704”—with an inflight-refueling probe, allowing the heavy, long-range copter to extend its flying distance even farther by drawing gas from an airborne tanker.

The retrofit—apparent in state-media photos—was further evidence of Tehran’s desperate yet resourceful efforts to maintain and even improve its bizarre, geriatric aerial arsenal. Iran’s air force is largely composed of pre-Islamic Revolution U.S. hardware from the 1970s plus Russian gear that Iran seized from Iraq.

But the addition of a refueling probe also raised a fascinating question. Five years later, Iran still has not admitted to possessing a tanker plane that can fly slow enough to refuel the RH-53D. Does the appearance of a probe-equipped helicopter indicate that Tehran is working on a new fleet of aerial tankers?

Tehran purchased six of the twin-engine RH-53Ds from Sikorsky before the 1979 revolution. But the complex machines—which can carry troops and supplies and also drag water-skimming minesweeping sleds—quickly fell into disrepair after most of the world imposed sanctions.

Lucky for Iran, in April 1980, U.S. Special Operations Forces left behind five intact RH-53Ds during their abortive—and, for some, fatal—attempt to rescue American hostages in Tehran.

Engineers at Iran’s state aviation enterprises pillaged the abandoned RH-53Ds for parts and brought the original six copters back to working condition—for a few years.

But by 1988, just one RH-53D was flightworthy. Tehran began acquiring spare parts illicitly from American and Singaporean agents working on Iran’s behalf.

In recent years, the Iranians not only restored the six original RH-53Ds—they also had enough parts left over to repair one of the copters the Americans had abandoned.

That boosted Tehran’s RH-53D fleet to seven machines. Based on their participation in certain war games—including the January naval exercise where “704” debuted its new refueling gear—the boxy copters apparently spend much of their time transporting Iranian commandos.

An RH-53D can travel more than 600 miles on internal fuel with a modest load. With aerial refueling, it could cover much, much more ground—flying until its lubricants ran low and its crew wore out. With inflight refueling, Iran’s RH-53Ds could carry out commando raids across the Middle East.

The U.S. military long ago fitted refueling probes to its own H-53 helicopters. But the Americans also bought special KC-130 prop-driven tanker planes that can fly slow enough—around 150 miles per hour—to allow the copters to plug their probes into the hoses the tankers trail behind them.

Iran has C-130s, but has not copped to modifying any of them for inflight refueling. Instead, Tehran continues to rely on four Boeing 707 tankers and the world’s only three 747-based tankers. It’s unlikely either of the Boeing jet models could safely fly slow enough to refuel a helicopter.

And that means one of two things. One—Tehran added a refueling probe to an RH-53D for experimental or even propaganda purposes and does not intend to deploy it operationally. Or two—Iran is also working on a new tanker probably based on the C-130.

David Axe is defense editor of The National Interest. He is the author of the graphic novels War Fix, War Is Boring and Machete Squad.

Image provided by the author