Not to scare people off but airlines in the US have very little supervision from the FAA or anyone else for that matter. The system functions on a self compliance and self reporting basis. The FAA does not have the people or budget to do more than a few spot checks. They rely on the individual airlines to certify they are in compliance and to self report any violations. I have not seen a FAA maintenance inspector checking aircraft in at least 5 years.
On the subject of safety and fuel the range of the aircraft relative to the route flown is not really a safety issue as long as there is no pressure on the crews to try and stretch the range. If you are not going to have the fuel required for a safe operation you divert to a closer field or plan a fuel stop. The published range of a airliner does not however equate to the operating range which can vary dramatically with weather and city pair involved. A 1600 mile published range may be less then 1000 miles in actual operations if you are flying into a high density airport with a forecast for poor weather.
G