SABENA is dropping Brussels flights to Gatwick this winter following disappointing interim results.
Services on the Brussels-Stansted route are also under threat after Sabena recorded a loss of £23m in the six months to June 30.
This compares with an operating profit of £13m in the corresponding period last year.
President and chief executive Paul Reutlinger said the carrier had no option but to cut poor- performing routes.
Both Gatwick and Stansted services are operated by Virgin Express under a codeshare agreement with Sabena.
Virgin Express has not commented on whether it will continue services on its own.