At first, the Swiss Air Force would shoot down planes which violated their airspace, but, after direct threats from Germany, they started forcing the planes to land instead. This came in handy for Allied forces whose planes were damaged after bombing runs. Instead of being captured as prisoners of war by the Axis forces, they would intentionally violate Swiss airspace.
Captured Allied forces were treated pretty nicely by the Swiss. They were interned at ski resorts which were empty due to a lack of tourism during the war. Over 100 Allied aircrafts and their crews were interned over the course of the war.
Due to Switzerland being surrounded by Axis-controlled countries, they were mistakenly bombed by Allied forces on more than one occasion. This led to strained relations between the Allied forces and the Swiss. The terms that were settled on were that single aircrafts violating their airspace would be captured, while bombing formations would be intercepted by their air force.
Many Americans tried to escape from their internment after D-Day so that they could help their comrades. The Swiss managed to recapture 183 of those 940 Americans. Those Americans were only released after the war when the US State Department lodged protests against the Swiss government to have them freed.
