There are two airports on the island of Tenerife, one on the north side (Tenerife Norte, TFN, also known as Aeropuerto de Los Rodeos) and the other one on the south of the island (Tenerife Sur, TFS, also known as Aeropuerto Reina Sofía). Both airports are at about 2.5 hours flying time from Madrid, and about 3 hours from Barcelona. San Cristóbal de La Laguna is 5 km away from TFN, and 65 km from TFS, with a motorway link covering the full journey in both cases. The easiest access is from the northern airport along the TF-5 motorway, and it takes about 10 min.
TFN handles mostly inter-island and domestic flights, with several daily connections to Madrid and Barcelona. If you connect there you may fly to TFN. TFS handles mainly tourist and low-cost flights, offering a large number of direct connections to many airports across Europe.