Delhi's Airport Metro Express will miss its August-end deadline set by the government for resumption of services as the repair work undertaken by Delhi Metro on the civil structure is expected to end only by mid-September.    The repair work on the bearings that serve as an interface between the pillar and girder is being undertaken by the Delhi Metro in coordination with authorities of the Reliance Infra-led Delhi Airport Metro Express that runs the line.    Nearly 500 of the 2,100 bearings were found to be faulty and the Delhi Metro in consultation with the Indian Railways has come out with specific designs to repair or replace the faulty bearings.    The 500 bearings would either be replaced or repaired according to their conditions, a top source told a leading news agency. The work is expected to end by September 20. Once it is done with the work, the authorities will hand over the line to the concessionaire.