At what altitude is the airstart procedure not recommended during engine failure procedures?

The airstart procedure during engine failure is generally not recommended below 2000 feet AGL due to several critical factors concerning safety and aircraft performance. At altitudes lower than this, the margin for error becomes significantly reduced, and pilots have limited time to successfully restart the engine and achieve controlled flight. The lower altitude means that if the airstart is unsuccessful, the available options for a safe landing are greatly diminished, leaving little room for maneuvering or troubleshooting.

In contrast, the other options suggest altitudes where the likelihood of successfully executing an airstart procedure is higher. Being above 3000 feet AGL allows for ample altitude to manage the situation and make decisions for a potential landing or redirecting flight, while sea level provides a sufficient altitude for recovery procedures and options. However, operating below 2000 feet AGL introduces an increased risk, thus making it the critical threshold for initiating an airstart.