A glass cockpit is a cockpit where flight data is shown on Electronic Flight Displays (EFDs) rather than separate gauges for each instrument. Examples of EFDs are the Primary Flight Display (PFD) which combines data from several instruments and is the pilot's primary source of flight information and the multi-function display (MFD) which allows data to be presented on multiple pages that are convenient to switch between. Another common name for these displays is Electronic Flight Instrument System (EFIS).
The use of electronic displays allows for better design solutions - the focus is shifted from trying to fit all necessary instruments into the small space of the cockpit to finding a way to present all importatnt information in a user-friendly way. Glass cockpits offer various benefits:
Values are easier to read both due to the lack of parallax errors (i.e. the reading does not depend on the angle a person looks at the instrument) and the use of precise numerical values (as opposed to an analog display). This allows pilots to more quickly interpret their speed, altitude, position, etc.
A flight display takes less space and is still able to show more information. This also helps pilots to quickly scan all data and assess the situation.
Electronic displays are linked to computers which allows data from multiple sources to be processed. As a result, data can be presented in ergonomic ways and warnings can be more noticeable.
Different layers of informaion can be presented. This is especially helpful for the horizontal situation display where data for e.g. weather, terrain, airspace and other aircraft can be displayed thus reducing the risks of entering thunderstorms, CFIT, airspace infringement and loss of separation.
As a result, glass cockpits are a popular choice in modern aircraft, both in the transport and the business aviation categories.
While electronic flight displays are considered more reliable compared to their mechanical counterparts due to the lack of moving elements, they are vulnerable to electrical system failures and software glitches. Therefore, in some aircraft analog altimeters as well as attitude and airspeed indicators as standby flight instruments in case the EFIS display failure.
An example of a glass cockpit with a PFD on the left, an MFD on the right and standby instruments below (on the left).