Tulsa's American Airlines base is the largest commercial aviation maintenance facility in the world.

It has more than three million square feet of hangar and shop space across 33 acres. 

Everything is stripped from the inside of the fuselage down to the floorboard and refurbished to make a plane that could be more than two decades old look and run like it's brand new.

Across the base, the engine shop may be the biggest source of pride for workers here.

The engine shop is working on 21 overhauls right now at a repair cost of $6 million an engine, and their workload is growing; 100 this year and double that by 2021.

The maintenance facility is a major contributor to the region's economy.

More than 5,000 people work there, and the work never stops. It goes on around the clock in three shifts, and the base is growing. More work means more workers.

According to ktul.com