AD2005 - Incident: Azul B734 at Sao Paulo on May 25th 2021 doesn't accept bus

An Azul Linhas Aereas Boeing 737-400 freighter, registration PR-AJY performing flight AD-2005 from Sao Paulo Viracopos,SP to Fortaleza,CE (Brazil) with 2 crew, was climbing out of Viracopos Airport when the crew stopped the climb at FL090 after receiving the message AC-Bus #1 was off. The crew worked the related checklists and returned to Viracopos for a safe landing about 25 minutes later.

Brazil's CENIPA reported generator #2 (right hand engine CFM56) did not automatically connect AC Bus #1 causing the bus to be off.

The aircraft returned to service about 27 hours later.