Few airline seats to be found as Miami evacuates Flights are sold out and standby lines are longer than ever.

 -- Residents and visitors of Miami are showing up to the airport in droves and finding very few seats available as Hurricane Irma approaches.

Despite airlines adding more than 10,000 additional seats by scheduling more flights and bigger aircraft out of South Florida since Wednesday, the demand is far outpacing the supply, airline officials told ABC News. Airline and airport officials say all flights are sold out, but they are working on bringing in additional planes to fly customers out.

Miami International Airport is urging people to book their reservation prior to going to the airport. If you don't have a reservation, please do not come, the airport said.

The last flight out of the major international gateway will be this evening, according to an airport spokesperson, but given the constantly changing nature of flights, it's not clear which one that will be.

The decision to cancel flights on Saturday and Sunday at Miami International was a decision made by the airlines, not the airport or the FAA.

A spokesperson for the airport told ABC News if passengers are stranded after the last flight leaves, they will be bused to a shelter.

If it is unsafe or not possible to do so, they will be centrally located in the airport.

Airports have comprehensive plans for situations like a major hurricane. Long before the storm arrives, airport personnel, food, water and other resources are prepositioned to last for days.

While an airport is generally a safe place to take shelter, officials ask that people do not come to the airport for that purpose. While they have supplies to take care of stranded passengers, they are not designed to be a shelter for large amounts of people.

While Ft. Lauderdale-Hollywood International Airport has already announced it will close this weekend, Miami International Airport says it has no intention to do so, saying it will close only if the airport suffers serious damage.