AMARI AIR BASE, Estonia — As NATO looks to replace its E-3A Airborne Warning and Control System (AWACS) fleet, it has asked operators for feedback on what technologies to incorporate in its future system.

While NATO leaders have not yet decided whether a single platform or a family of systems will take over the early airborne warning mission, "I think the most essential thing is the capability ... be absolutely interoperable. I think that’s the key, that is the most essential thing,” said Lt. Col. Hans Growla, a crew member and public affairs officer for the NATO E-3A component in Geilenkirchen, Germany.

But Growla declined to comment on what specific technologies could be integrated into an AWACS replacement to grow its capability, citing sensitivities.

NATO’s tanker, AWACS programs see membership increase Canada has decided to rejoin NATO’s airborne warning and control system program program, while Belgium has agreed to buy into the alliance’s tanker program — a pair of moves expected to strengthen NATO’s indigenous air capability.

In June, the head of the NATO organization that manages the E-3A inventory told Reuters that the organization was racing against the clock to choose an AWACS replacement.

NATO plans to spend $750 million for the final service life extension of the aircraft, which would keep it flying until 2035, said Michael Gschossmann, director of the NATO Airborne Early Warning and Control Programme Management Agency. But if it delays making a decision on a replacement for too long, it could get stuck paying for additional work on the current E-3A aircraft.

“We have to get moving on this. We have to ensure that the studies move along quickly. We need a reality check,” he said.

One option, Gschossmann said, would be to purchase the E-7 Wedgetail, a Boeing aircraft currently operated by Australia, Turkey and South Korea. The United Kingdom also plans to purchase the aircraft. “That would give us a basic capability that could be expanded in the future,” he said.

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Like the units that conduct Baltic air policing, the NATO E-3A component has found itself similarly taxed after the Russian annexation of Crimea in 2014, with the number of surveillance missions increasing.

“There is a clear shift from training to real world missions/operations,” Growla said, with a growing presence over the skies of Poland, Romania and Bulgaria. “Flying in northeast Poland gives you a great view into the Baltic states. We don’t need to be physically flying in the airspace of the Baltics, we can stay a bit more south and see everything.”

Despite the high operational tempo, Growla said NATO’s E-3A component is making do with its 14 AWACS planes.

“The Ukraine crisis was starting when we were still deployed to Afghanistan. … [For a time] we had more or less two tasking, and then ISIL," he said, using an acronym for the Islamic State group. "We were really busy.”

Currently, 17 nations participate in NATO’s early-warning-and-control force, which operates 14 E-3As and six E-3Ds: Belgium, the Czech Republic, Denmark, Germany, Greece, Hungary, Italy, Luxembourg, the Netherlands, Norway, Poland, Portugal, Romania, Spain, Turkey, the United Kingdom and the United States. Canada announced in February it would rejoin the NATO E-3A mission, after dropping out in 2014 to cut costs.

Earlier this year, NATO wrapped up a two-year-long effort to modernize its E-3A aircraft, replacing the fleet’s 1970s-era flight instruments with glass cockpits that include five full-color displays and modern avionics that are easier to maintain.

One of those upgraded AWACS planes made the trip to Amari Air Base, Estonia, for an air show commemorating the Estonian Air Force’s 100th anniversary. It was the first open display of a NATO E-3A in Estonia, with visitors able to walk inside the aircraft to view the cockpit and crew stations.