London Southend Airport

Global figures show, London Southend Airport (IATA Code: SEN) welcomed 2,035,535 (Wikipedia) passengers through its doors in 2019. The airport itself sits to the north of Southend-on-Sea, separated from the town of its namesake by the A127, which joins the M25 at junction 29, north of the Dartford Thames river crossing. Most aircraft operating at the airport are mostly short regional flights or short-haul international flights to destinations such as the north of Spain, Bilbao and the south of France. Most Aircraft are operated by either EasyJet, and their small A320NEO family aircraft and Flybe, who operate turboprop aircraft that have a maximum capacity of just over 60 people. Therefore, due to the airport's short runway, much like London City Airport's (IATA Code: LCY), larger wide-bodied aircraft produced to serve long-haul routes, such as the A350, A380, Boeing 747 and Boeing 777, are unable to land at the airport. As a result, the airport is limited by the runway size, along with it's sole terminal's floor space to become a destination to many more tourists from around the United Kingdom and the rest of the World. 
Another limiting factor is it's accessibility from central London, as larger airports such as Heathrow, Gatwick and Stanstead are easier and quicker to access due to the infrastructure already in place, such as the M25, M23 and M11 respectively, whereas the A127 doesn't have the capacity of the M25 or M23, due to its 2 lanes and 50 mph national speed limit. Southend Airport's location puts it at a great disadvantage too, as many larger airports are closer to the touristic hub of central London, as tourists and visitors have greater ease of access to central London.