American Flight Support is an official registered agent with Guatemalan CAA and can get you landing or overflying permits within 48 hours. You have to use an agent as there are many pieces of paperwork you need to fill out to obtain the permits. Whether you are flying parts 121, 135, and 91, you still need permits to land and overfly.
Please Note: They require two days notice for your application and do not work over weekends. CAA is usually not responsive to pilots. Please Send all your inquiries to ops@americanflightsupport.com