Firefly (FY, Penang) resumed narrowbody jet operations on May 3, 2021, using a single B737-800 transferred from its parent Malaysia Airlines.

9M-MXF (msn 40133), a 9.6-year-old aircraft ordered by and delivered new to Malaysia Airlines, was retired by the flag carrier on December 12, 2020, Flightradar24 ADS-B data shows. It was reactivated on April 30 for test flights after transfer to Firefly. On May 3, it operated the first revenue flight from Penang to Johor Bahru and return.

Firefly said that during May, it would start running its B737-800s from Penang to Johor Bahru in southern peninsular Malaysia, and Kuching and Kota Kinabalu on Borneo. However, the first flight to Kota Kinabalu, which was due to take place on May 3, was cancelled, while services to Kuching have yet to be formally scheduled.

The second and third B737-800s to be transferred to Firefly, 9M-MXU (msn 40158) and 9M-MXV (msn 40159), were ferried to Penang on May 1 and May 3, respectively, but have yet to enter service for the carrier. Going forward, Firefly plans to increase its fleet of Boeing narrowbodies to up to ten units.

According to the ch-aviation fleets history module, this is Firefly's second foray into the jet niche as it had operated two B737-400s between 2011 and 2014.

Thus far, Firefly has operated as the regional subsidiary of Malaysia Airlines, deploying twelve ATR72-500s on a largely point-to-point domestic network centred on Kuala Lumpur Subang and Penang. While retaining its domestic turboprop network (which also used to include services to Singapore Seletar, Banda Aceh in Indonesia, and destinations in southern Thailand prior to the COVID-19 pandemic), Firefly will develop a hub-and-spoke domestic and international network operated with the B737-800s stationed out of Penang to complement the network of its parent centred on Kuala Lumpur Int'l.

Malaysia Airlines itself continues to operate forty-four B737-800s, of which around a half is currently in storage due to the lack of international opportunities. The carrier has twenty-five B737-8s on firm order from the manufacturer.