A coolant interlock was a sealant on Federation shuttlecraft, used to keep plasma from leaking out of the nacelles.

While undergoing an investigation of the death of Cadet Joshua Albert in a shuttle accident in 2368 on the USS Enterprise-D, Lieutenant Commanders Geordi La Forge and Data discovered that Wesley Crusher's shuttle's coolant interlock was left open while he was flying it, which they both found unusual. Captain Jean-Luc Picard realized that Crusher and his team, Nova Squadron, deliberately left their coolant interlocks open, so they could ignite the plasma and perform the "Kolvoord Starburst", a maneuver banned from Starfleet Academy since the 23rd century. Unfortunately, this attempt at the maneuver was what caused the death of Albert. (TNG: "The First Duty")