The A-320 aircraft, with engineering material, full meal for the passengers and crew and technical staff left Delhi at 1145 hours, officials said, adding provisions have also been made there for refuelling of both the planes.
The relief plane was earlier supposed to leave Delhi at 1045 hours, but its departure was delayed by an hour as several clearances were required for this special flight, they said.
The relief plane would fly back the passengers and crew members and is expected to arrive here by 1600 hours, the officials said, adding that necessary repairs would be undertaken in the other aircraft by the Indian engineers and technical staff before it flies back here.
"We are sending engineers and the problems with hydraulic system will be checked," Civil Aviation Minister Ajit Singh told reporters here.
Earlier, the New Delhi-bound A-319, with 128 people on board, made an emergency landing at Nawabshah airport in Pakistan's southern Sindh province after developing a serious fault in its hydraulic system this morning.
All 122 passengers and six crew members on board the Airbus 319 aircraft are safe, officials said. Meanwhile, Simran Singh of Patiala, who was at the IGI Airport here to pick up his mother, said that he reached the airport at 2.30 AM as the plane was supposed to land at 4 AM.
"We were told over an hour later that the plane had landed somewhere in Pakistan," he said, adding the aircraft was carrying many passengers from Punjab. He said his mother Jaspal Kaur was coming from Toronto and had taken the connecting Air India flight from Abu Dhabi to New Delhi.