Overview
- On December 18, Volaris El Salvador flight 4321 off runway 33L was cleared to turn left to heading 110 as United Express flight 4814 off 33R was cleared to turn right to heading 340.
- The Volaris A320neo instead began a right turn toward the other departure path despite a correct readback of the left-turn instruction.
- Both aircraft received collision alerts, and the United Express crew reported a TCAS Resolution Advisory with the conflict peaking around 1,200–1,300 feet.
- Tower communications captured an initial "stand by" response and nonstandard phraseology, with reporting noting a delayed recognition of the developing conflict.
- Commentary points to risk from non‑intuitive long-way-around headings and suggests mitigations such as intermediate headings, explicit "long way around" wording, or published RNAV SIDs, with no official investigation findings reported yet.