Note: Just a simple ‘need to know’ fact from the examiner…

In general, no aircraft shall operate below FL100 (10 000 feet MSL) at an indicated airspeed of more than 250 kts.

This restriction is primarily in place to enhance safety in congested lower altitudes by providing pilots with more time for "see and avoid" manoeuvres and reducing the impact of potential bird strikes.

Exceptions include: 

• If an aircraft's minimum safe manoeuvring speed (e.g., for heavy jets) is higher than the prescribed limit, the pilot may operate at that minimum safe speed, 
• or for military aircraft if operational considerations require higher speeds.