Before 2011, Atlantic Southeast had the IATA 2-letter code "EV". Then,
On November 22, 2011, both ExpressJet and Atlantic Southeast Airlines achieved a single operating certificate that allowed them to operate as one carrier, using Atlantic Southeast's former call sign "Acey". Effective December 31, 2011, all flights began operating under the name ExpressJet.[7] ExpressJet currently operates as United Airlines Express.
(so says Wikipedia.)
What IATA code(s) did ExpressJet, or airlines which became ExpressJet, use until that time?