Russian fighter planes have circled a US-based air base in Syria several times in March. This could increase tensions following the downing of a US drone over the Black Sea last week.

According to NBC News, Russian planes have flown over a US base in Syria more than 25 time this month. This violates a 2019 agreement between Russia and the US over the use of Syrian airspace where each country has military outposts.

Lt. Gen. Alexus Grynkewich is the commander of the combined forces air components for US Central Command. He stated that flights increased in March.

Two Russian Su-27 fighter planes approached the US and poured fuel on it. They then crashed into a US MQ-9 Reaper drone above the Black Sea. The US was forced to take down the drone.

Grynkewich stated that the “uncomfortable” situation in Syria was caused by Russian jets flying over the US’ At Tanf Garrison post.

Grynkewich stated to NBC News that they fly regularly directly overhead our units. I have defined directly overhead as being within a distance of about a mile and no more than a half mile off one side, while we have forces right there on ground.” It’s an unpleasant situation.

According to NBC News in January, Russian forces circled US airbase 14 more times. They did not fly over it in February.

Grynkewich stated that it increases the chance of miscalculation and, given events like the MQ-9 accident in the Black Sea (MQ-9), it’s not behavior I would expect from a professional Air Force.”

Insider reached out to the Pentagon and US CENTCOM for comment but they did not respond immediately.

Since at least 2015, both the US and Russian troops have been in Syria. According to NBC News the US established a phone line to deconflict with Russia to ease tensions. However, Russian military personnel over the calls with the US have stated that they do not recognize the US airspace or base.

Grynkewich said that the Russians had abandoned the protocol tenet over the past few months.