When must a pilot file a DVFR flight plan?

A pilot must file a DVFR (Defense Visual Flight Rules) flight plan when flying into a designated Air Defense Identification Zone (ADIZ). An ADIZ is a specially established airspace in which the identification and location of aircraft are required for national security reasons. Filing a DVFR flight plan allows air traffic control and the military to track flights entering this sensitive area, helping to ensure the safety and security of the national airspace.

This requirement is critical because without proper identification and communication, a pilot could unknowingly enter restricted airspace or create a situation that poses a security threat. The DVFR flight plan also provides pertinent flight information to ATC, which is essential for both operational and emergency response purposes.

In contrast, the other options do not require filing a DVFR flight plan. Flying into a controlled airport typically requires a standard VFR or IFR flight plan but not specifically a DVFR. Experiencing engine failure does not inherently require filing a DVFR; rather, it necessitates emergency procedures based on the situation. Lastly, flying VFR in congested airspace has its own set of regulations and does not pertain to a DVFR flight plan unless flying into an ADIZ.