Jets from RAF Leuchars have been scrambled almost 50 times in the last five years to intercept Russian military aircraft.
Tornado F3s were launched from the Fife airbase on Monday and Tuesday after the planes were detected in international airspace around the UK.
The second came hours before the UK Government announced defence spending cuts which appear to have spared Leuchars.
It emerged yesterday that before this week’s alerts the 48th and 49th since the beginning of 2006 RAF Leuchars had stepped into action six times due to Russian aircraft this year.
There were 11 interceptions last year and activity peaked in 2007, when Leuchars crews launched 19 times.
Such flights were common during the cold war, when the Russians used to test the reactions of British forces.
St Andrews University international relations and terrorism specialist Professor Paul Wilkinson said the frequency of such incidents was significant and underlined the importance of maintaining the country’s air defence.
He said, “The number of interceptions of that kind indicate how much another country is trying to penetrate our airspace and prove it can do so without being intercepted.
“They are a very good guide to the degree which we are successfully monitoring our own airspace. They show that we really need to be very careful in reviewing our air defences, that we don’t overlook the importance of air defence.
“We must have the resources, the aircraft and the manpower to maintain air defence at a reasonable level.”
The Russians are entitled to fly in the NATO air policing area but are intercepted when they cannot be identified and RAF jets will maintain contact with them until they leave the UK area.
Defending UK airspace is the responsibility of two RAF bases Leuchars in the north and Coningsby in the south.
The duty, known as quick reaction alert, means the base has crews on permanent to launch with 10 minutes’ notice to intercept unidentified aircraft.
It is to be taken over from 111 Fighter Squadron by the new Typhoon squadron, 6 Squadron, in March.
The MoD was unable to provide details of the incidents, but a spokesman said, “We can confirm that Tornado aircraft from RAF Leuchars were launched to determine the identity of unknown aircraft…
“The aircraft were subsequently identified as Russian military aircraft.”