How long must the cabin lights be at maximum brightness after takeoff?

The correct duration for maintaining cabin lights at maximum brightness after takeoff is 15 minutes to ensure safety and comfort for passengers and crew. This period allows for visibility in the cabin, enabling crew members to conduct necessary post-takeoff safety checks and attend to any immediate needs of the passengers.

Having cabin lights at maximum brightness during this time is essential for two main reasons: first, it enhances visibility in case of any emergencies that might occur shortly after takeoff. Second, it helps in acclimating passengers to the flight environment, which is particularly important following the intense lighting conditions during takeoff.

The other options suggest either shorter or longer durations, which may not align with the recommended safety protocols established for aviation operations.