I remember reading a whole lot ago (so I am currently unable to find the reference, sorry) that during WWII, British aircraft would return from missions at a specific speed that was unattainable from German aircraft, i.e. it was either too fast for some, or too slow for others.

This had the immediate benefit of enabling radar operators to distinguish friends from foes without the need of any additional equipment or method, they would simply compute the aircraft speed and determine if the aircraft was British or German.

Is it true? What was that speed?
Why wasn't there a German aircraft capable of flying at that speed?

  • 2
    $\begingroup$ I recall reading something similar: designated location/course/speed/altitude combinations that were given to RAF pilots secretly and which served as a "Don't shoot me" to radar and AAA gunners. If I can find a reference I'll post it up. $\endgroup$
    – Steve V.
    Apr 10, 2017 at 16:09
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    $\begingroup$ British pilots could squawk their parrot, the ancestor of IFF. $\endgroup$
    – mins
    Apr 10, 2017 at 17:09

2 Answers 2


Ground speed

Real time wind components were not available to the pilots. They wouldn't have been able to tell the ground speed. Especially over the English Channel on a calm or foggy day where a drift meter is not very useful (if equipped).

[A drift meter] indicates the aircraft's drift angle due to winds aloft, and can be used to calculate the ground speed.

If they flew at an agreed true airspeed, then the controllers wouldn't have been able to tell that true airspeed.

Early IFF

Looking into the history of IFF and radar in WWII, it's apparent from early on radio IFF was used. It started with the pip-squeak system.

Mistaken identity

In the Battle of Barking Creek a radar issue caused a friendly fire incident where returning British fighters were attacked. According to Wikipedia, as of 2010 the final report has not been declassified yet.

Another one was the air attack on the fortress of Koepenick, the Germans thought there was an air raid en-route, they launched fighters, only to mistake their fighters for the raid, only to send more fighters, etc. And there was no raid, just the Americans were returning from a bombing mission and judging their direction of flight aurally led to this confusion. The German fighters started to run out of fuel and landed.

Göring freely admitted the laugh was on him, that he had sent the Luftwaffe on a mammoth tour of their own air space.


Wind and ground speed aside, if we say it was a certain route combined with speed, that would require a level of area navigation that just wasn't there in WWII.


Logistically, when an operation is launched, the air command has an idea of when to expect its return.


Comparing the Focke-Wulf Fw 190 with the Supermarine Spitfire, the German Fw 190 was faster. 426 mph compared to 370 mph.

As for slow speeds, slow flying on the return leg is just calling for the surviving planes to be caught up with and shot down.

I'm calling it myth busted.


I was a light attack jet pilot aboard the USS Nimitz during the 1980's. I did 2 cruises in the Mediterranean and was airborne during the initial shoot down of the Libyan MIG's. We also spent time off Beirut after Sadat was assasinated. We came close to initiating strikes against one country during my tenure. I say this just to make the point that I have operational experience.

We had procedures for coming back to the ship during times of threat. They included flight paths for approaching the carrier. If you were obeying the procedures you would be identified as a friendly aircraft. Airspeeds were a part of the flight path, but they had little to do with the capabilities of adversarial aircraft. I do remember the airspeeds were slow making our aircraft vulnerable to attack. My guess is that they would engage the threat separately.


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