The sentence that most suitably fills the space is: Our plane was scheduled to take off at 10:00 hrs but it was delayed because of the bad weather.

In the context of aviation, “take off” is the correct term used to describe the action of an airplane leaving the ground and starting its flight.

This term is universally used in the aviation industry and is understood by passengers, crew, and air traffic control.

For example, consider these sentences:

1. The pilot announced that we were cleared for take off.
2. The flight was delayed, so we didn’t take off until an hour after our scheduled departure time.

The other options, while they might be used colloquially, are not the standard terms used in aviation.

“Fly out” and “start out” are more general terms and could refer to the start of any journey, not specifically a flight. “Shoot off” is often used to describe someone leaving quickly, but it’s informal and not specific to aviation.

“Lift off” is more commonly used in the context of spacecraft, not airplanes. Therefore, “take off” is the most suitable option for this sentence.