What is the floor of Class E airspace when designated in conjunction with an airway?

In the context of Class E airspace, when it is designated in conjunction with an airway, the floor of that airspace is at 1,200 feet above ground level (AGL). This is a standard for airspace classification intended to provide controlled airspace above a certain altitude to separate IFR (Instrument Flight Rules) traffic from VFR (Visual Flight Rules) traffic and to ensure safe operations within designated airways.

Class E airspace begins at different altitudes depending on the context, but when it is linked to airways, it is specifically set to start at 1,200 feet AGL to align with the operations of IFR aircraft that use these airways. This altitude enables effective vertical separation between different classes of traffic, allowing for safe navigation within the controlled airspace.

In contrast, other options present altitudes that do not align with the regulations governing the structure of Class E airspace in relation to airways. Therefore, the designation of 1,200 feet AGL serves as the appropriate floor for Class E airspace when associated with airways, maintaining the safety and efficiency of air traffic.