An intruder was killed on a Denver runway after exploiting a security gap at one of the nation’s busiest airports.

The decision by Alaska Airlines to stop flying one of its planes over the Pacific Ocean to Hawaii due to warnings from a cabin-pressurization system — yet keep flying it over land — is raising questions about whether the jet should have been in the air at all.

A North Dakota state senator took off from a remote Utah airport last month with his wife and two young sons in the plane without the runway lights on a dark night with no moonlight and crashed just a minute later killing everyone aboard.

While the cause of a deadly collision between two vintage military aircraft at a Dallas air show to commemorate Veterans Day remains unknown, experts say the accident will likely renew discussion over whether additional safety rules are needed for such events.