It's not confirmed yet that it was a russian missile. If it was - NATO should react strongly (by introducing no-flight zone over Ukraine at the very least - it

It's not confirmed yet that it was a russian missile. If it was - NATO should react strongly (by introducing no-flight zone over Ukraine at the very least - it is impossible to stop missiles flying over Ukraine if we only shot down once they cross the border). Otherwise Russia will test the collective defense more over time. After Turkey shot down a russian bomber that one time in 2015 there was no further russian military planes flying over Turkey without permission.