Two Airbus A330 MRTT tanker planes, one French and one NATO, were spotted on 22 October over the western Black Sea, east of the Bulgarian coast and not far from Burgas, public flight-tracking data show.
Their routes match air-to-air refuelling flights. The fighter jets that probably took on fuel cannot be identified on public platforms. NATO's Steadfast Noon exercise had ended two days earlier.
The French tanker, registration F-UJCO and callsign FAF4091, took off from Istres air base in southern France, the main hub for French tankers and transport planes. The route map shows it crossed the Balkans and Romania to reach the western Black Sea.
The second plane belongs to NATO's Multinational MRTT Fleet (registration T-056, callsign MMF65). It took off from Cologne in Germany and was tracked over the Black Sea. The two tankers flew close together in a similar area.
A specialist website that tracks military aircraft and ships from open data says the two planes show that both national and multinational tankers are available on NATO's eastern flank. It says the flights confirm the need for air-to-air refuelling in the alliance's operations in the region.
Fighter jets that do not show up on tracking platforms are not unusual in military operations, the site's authors say. Military aircraft can fly without broadcasting their position to civilian tracking networks, so open data makes it hard to tell how many there are, what type they are and which country they belong to.
Still, the tanker routes give useful clues about military activity in the area, the authors write. Refuelling in the air extends the flight time and range of fighter jets and lets them stay in the area without returning to base.
NATO is stepping up patrols and surveillance over the Black Sea because of Russian attacks on merchant ships. In early October, air and sea drones attacked two merchant ships in Bulgaria's exclusive economic zone, and one of them sank. Other attacks followed in the next days, some with deaths, off the Bulgarian and Romanian coasts, including on ships in Romanian territorial waters.
A US Navy Boeing P-8A Poseidon arrived in Varna on 18 October. It flew in from Sigonella naval air station in Italy for a mission over the western Black Sea.
On 21 October we reported that Bulgaria's air force had stepped up surveillance over the Black Sea, with F-16, MiG-29, Su-25 and L-39 crews patrolling and scouting the airspace above the territorial sea. The same day, a US C-17 landed at Sarafovo airport in Burgas.
Bulgarian F-16, MiG-29, Su-25 and L-39 military aircraft are also patrolling, observing and scouting over Bulgaria's territorial waters.