The answer is really easy: Guatemala City.
Tegucigalpa is also in need of a better infrastructure, but it doesn't have the traffic volume Guatemala City has.
is served by many types of aircraft, such as:
DC9-50 Tikal Jets
A320-200 Taca, Mexicana
A300-600 American Airlines
B737-700/800 American Airlines, Continental, Copa
B757-200 Delta, United, American, UPS
B767-300 Lan Chile (Cargo) and MasAir Cargo (not sure if this one is still flying)
B747-200 Atlas Air and some other cargo airlines
MD11 Martinair Cargo
It's also visited by some USAF
's C-5 Galaxy as well as Volga Dnepr's An-124s from time to time.
In the past, GUA
has been served also by KLM's 747-400s and DC-10s, Pan Am's A300s, 747s and Iberia's DC-10s and 747-200s.
However, ther terminal, built in the late 60s has never been improved, modernized or expanded, except for:
Some some updates to the arrivals area.
A few paint works inside.
The replacement of some ceilings .
A couple of new restrooms (which look horrible already).
Installation of 8 jetways.
Apart form that...the terminal is old, small and crowded. It must have been a "state-of-the-art" terminal back in the 60s when it was opened as the design looks quite "revolutionary" for that time, but almost 40 years have passed and the building has become old.
In addition, it's location inside the city which at the same time is inside a valley, and it's runway length (about 9228 ft...not bad if it was at sea level, but it is at 5,000 ft. ASL) make it neccesary to think about a new airport for Guatemala's capital.
Many things have been said through the years about a hypothetical new airport, but they are just intentions...nothing has been made.
On the contrary, we can see the examples of San Salvador and San José, both cities having "first class" airports: San Salvador built a new airport while San José's was completely re-designed and expanded.
[Edited 2005-05-21 00:02:48]