Mexicana wanted to operate their 727-264s without takeoff performance payload restrictions in “high-and-hot” conditions ... Boeing accommodated by certifying what was essentially a RATO (Rocket-Assisted Take Off) capability: I believe there were six “rocket bottles” installed in the aft wing-to-body fairing (three per side) that were available to provide supplemental thrust in the event of an engine failure on takeoff

there are a handful of photos of MX 72S takeoffs with the rockets firing; I’m not sure if the pilots actually had to engage the system for takeoff or manually activate it as part of the engine failure recovery checklist
https://www.avgeekery.com/boeing-act...fs-on-the-727/