Braking action in aviation is a description of how easily an aircraft can stop after landing on a runway. Either pilots or airport management can report the braking action according to the U.S. Federal Aviation Administration. When reporting braking action, any of the following terms may be used: Good; Medium; Poor; Nil - bad or no braking action. If an air traffic controller receives a braking action report worse than good, a Pilot Report (PIREP) must be completed and an advisory must be included in the Automatic Terminal Information Service ("Braking Action Advisories are in effect"). As of October 2019, the FAA has used mu values to describe braking conditions Europe In Europe this differs from the above reference. Braking action reports in Europe are an indication/declaration of reduced friction on a runway due to runway contamination (see Landing performance, under the Runway Surface section) which may impact an aircraft's crosswind limits. European reports have nothing to do with stopping distances on a runway, though they should alert pilots that stopping distances will also be affected. Landing distances are empirically dealt with by landing performance data on dry/wet/contaminated runways for each aircraft type. Crosswind limits Whenever braking actions are issued, they are informing pilots that the aircraft maximum crosswind limits may have to be reduced on that runway because of reduced surface friction (grip). This should alert pilots that they may experience lateral/directional control issues during the landing roll-out. In a crosswind landing, the pilot tacks into wind to make allowances for the sideways force that is being applied to the aircraft (also known as using a crab angle). This sideways force occurs as the wind strikes the aircraft's vertical fin causing the aircraft to weathercock or weathervane. This manifests itself as an angular displacement of the fuselage relative to the runway centreline. This angular displacement is known as drift angle. Just before or upon initial ground contact, the pilot must re-align the fuselage to zero the drift angle (i.e. correct it to parallel with the runway's centreline). This re-alignment is accomplished using the rudder flight control surface. As the wheels make contact with the runway surface there are a lot of side forces and torsion placed on the tyres due to them countering the weathervane effect which continues to try to act upon the aircraft. A combination inherent strength of the tyres and the action of the runway surface