Germany has grounded all of its Typhoon jet fighters because of reliability problems with the ejector seat. While the Typhoon is a new design, older models of Western and Russian aircraft have had a lot of mass groundings in the last few years over safety issues. With new aircraft, the groundings are often because a possible flaw was discovered in an infrequently used piece of equipment (like the ejection seat.) There have been several recent Typhoon accidents where the ejection seat did not perform as it should have.
Ejection seat costs between $200,00-300,000. While some models of ejection seats are used in many different aircraft, each aircraft type requires that the seat be customized for the shape, and other peculiarities of that warplane. This introduces more areas where something can go wrong. Most ejection seats weigh about half a ton, and are complex bits of technology. Ejection seats became essential as military aircraft became so fast, that a pilot could not safely climb out of the cockpit and jump. With the higher speed, there was the danger of hitting the tail. Also, escaping pilots were often injured or stunned, and unable to get out quickly enough.
The first ejection seat design was developed in Germany, where the seats were first installed in their He 219 night fighters, in 1943. These used compressed air to propel the seat out of the aircraft. A year later, rocket propelled seats were installed in the He-162 jet fighter. By the end of the war, all of Germany's jets were equipped with rocket propelled ejection seats.
While the Swedish firm SAAB had also developed a rocket propelled ejection seat, it was British firm Martin-Baker that jumped in and created a design that quickly filled the needs of most Western air forces. Martin-Baker supplies about two-thirds of the ejection seats for Western fighter aircraft, including the Mk-16A model used in the Typhoon. Over 10,000 aircrew have successfully used ejection seats since World War II.