Fighter and attack squadrons on two U.S. aircraft carriers — one engaged in operations against ISIS, the other on station in the restive West Pacific — have resorted to extraordinary measures to keep their pilots safe from persistent oxygen-supply problems in the Navy’s go-to carrier aircraft, the F-18 Hornet.

Aboard the USS George H.W. Bush in the Persian Gulf, Military.com’s Hope Hedge-Seck reports that the Bush and USS Carl Vinson both deployed in January with hyperbaric chambers, “slam sticks,” and even store-bought Garmin wristwatches to ward off the widespread oxygen problems which have plagued the fleet’s jet trainer aircraft, the F/A-18E and F Super Hornet variants, and the related E/A-18 Growler electronic warfare aircraft.

The Bush has already had to use its hyperbaric chamber twice to treat pilots “who experience[d] hypoxia-like symptoms in the cockpit,” reports Seck: once in February, when a two-person Growler crew experienced “an ‘abnormality’ with the aircraft’s environmental control system,” and again in April, when a solo F/A-18 pilot became disoriented shortly after takeoff.

Both aircraft trapped safely on the deck, and the pilots recovered fully after pressure treatment in the chamber, according to Capt. James McCall, CO of the Bush’s Carrier Air Wing 8.

The chambers were installed on both carriers as the result of “a dialogue from aviators in squadrons right to the three-star level,” McCall said. Navy-wide, that dialogue has proven testy: Aviators in the service’s go-to training aircraft, the T-45 Goshawk, went on strike in April to protest problems with the aircraft’s environmental control systems that can cause disorienting oxygen shortness and even death.

But more remarkable than the presence of hyperbaric chambers are the other DIY fail-safes that squadrons have fashioned to avoid oxygen problems on 10-hour sorties over Iraq and Syria, Hedge-Seck reports:

McCall said the carrier was the first to deploy its fighters equipped with “slam sticks,” small devices that measure cockpit air pressure and other factors, and can provide diagnostics following a mission…

Another measure, designed to help pilots detect cockpit problems before they can physically feel them, is a true improvisation: the wearing of commercially available Garmin watches, equipped with altimeters and barometric sensors, that can be set to sound alarms when certain thresholds are reached.

“Some of our aircrew had Garmin watches that they had bought, watches with little altimeters on them,” McCall said. “I think somebody was just like, ‘Hey, this would make sense.’ And so we offered up discussions with one of my [commanding officers] and myself, and we said, ‘Let’s pitch this up the chain of command.’ “

Congressional testimony in March revealed that the Hornet and Growler platforms have experienced more than 400 critical incidents in recent years, chiefly oxygen-supply and cabin-pressure issues.

In response, the Navy is currently conducting a monthlong review of all the issues on F-18 and T-45 aircraft and has deployed “an Aero-Medical Crisis Action Team (A-CAT) consisting of flight doctors, physiologists, toxicologists, engineers and specialists” to tackle the problems, according to Aviation International News.

That report added that the Air Force — which experienced similar hypoxia issues in its F-22 Raptor, linked to at least one pilot fatality — “has offered to provide the Navy with an in-line air quality sensor previously approved for use on the F-16 Fighting Falcon.”