Which is the fastest aircraft and at what speed can it fly?

In the search for the speed of the fastest airplane in air speed, the first problem was to find the difference between regular speed and air speed. Air speed is defined as the speed of an airplane with relation to the air, as compared to regular speed, which is the speed relative to the earth.

In 1968, according to the Guinness Book of World Records, a record airspeed of 2,070.102 mph (925 m/s) was achieved by a Lockheed YF-12A. The 1989 Guinness Book states that a record airspeed of 2,193.167 mph (980 m/s) was achieved by a Lockheed SR-71-A, which is a newer version of the YF-12A. The online source from the AFAM web page agrees with this number to the thousandths place, and it was recorded 7 years later. As it says, this plane has held this record speed for 24 years. The 1996 World Book Encyclopedia has a different answer of 4,520 mph (2020 m/s). This difference in opinion can be explained by the fact that this record speed was performed by a rocket plane, which differs from the type of plane mentioned in the other sources.

The source from 1968 differs from the more recent data because since 1968, engines and designs of planes have been advanced due to technological advances so that planes can fly faster. Of course there are other faster speeds. The US Space Shuttle flew at a record 16,000 mph (7153 m/s). These machines aren't planes and they achieve these high speeds only during reentry.