The US Department of Transportation's Federal Aviation Administration (FAA) has proposed a $917,000 civil penalty against three of Puerto Rico Ports Authority's commercial airports.
The penalty has been proposed against the airports for violating aircraft rescue and firefighting (ARFF) norms.
FAA Administrator Michael Huerta said: "Maintaining required aircraft rescue and firefighting capabilities is critical to safe airport operations.
"Emergency response is one of the most important safety functions that commercial airports perform."
Several allegations have been charged against the three airports, Rafael Hernandez Airport, Mercedita Airport and Antonio Rivera Rodriguez Airport.
The Rafael Hernandez Airport was charged due to its failure to deliver required ARFF capabilities.
The airport requires two aircraft rescue and firefighting (ARFF) vehicles, but on 25 March 2015, one of the two vehicles failed to perform its function as it could not correctly combine firefighting foam and water.
A member of ARFF staff at the same airport also broke the rules by failing to apply extinguishing agent within three minutes of an alarm sounding.
One of the firefighters wore a damaged fire suit and was therefore was not equipped to properly perform his duties.
The airport also failed to provide recurrent aircraft familiarisation training to 13 of its firefighters, and did not inspect its tenant fueling facilities between July 2014 and March 2015.
Rafael Hernandez Airport conducted 14 of its daily self-inspections at night rather than at sunrise, and kept a non-functioning ARFF vehicle.
In March 2015, the Mercedita Airport conducted nine of its daily self-inspections in the afternoon or at night and not at sunrise, as specified in its airport certification manual.
During the same month, the ARFF vehicles at Antonio Rivera Rodriguez Airport did not posses two-way radio communications with its fire station.