The last thing happened at April 5th 1994 during a low-level mission in a F-5B of the Spanish Airforce. On it's way to the target the plane hits a big bird. Parts of the bird and the windscreen came in the cockpit. The frontseat pilot in this case is a very lucky man. At the moment of impact he bend over to grab something or so. But unfortunualy the backseater is hit by the parts. He got some major injuries (his hand and arm were broken and he lost his left eye). Wearing his visor down it prevented to become worser. After a safe emergency landing at their homebase technicians find out both ejection seats become useless by the result of the impact so escaping by using the ejection seats was impossible.

This is one of the reasons why aircrew wear helmets. A flighthelmet is a safety product. When they're not meet the specifications anymore they will be scrapped or sold as a surplus helmet. This is why we have the disclaimer on this website. Don't use your surplus helmet as a safety product during a backseatride or just when you make a trip on your motorbike.  A surplus helmet is no safety product anymore! Charles Rudolf from Gentex told me the following story: "We have heard that the US Government has just recently decided to no longer provide surplus or used helmets to the market, due to a court case resulting from misuse of a flight helmet (as a motorcycle helmet). We are trying to verify this information". 

Source: Spanish Airforce, 'Veilig vliegen' magazine, Gentex corp.