A mid-air collision between two IndiGo planes, carrying over 225 passengers and crew, was averted over Guwahati after a pilot of one of the flight steered away his aircraft to a safe distance when they came perilously close to each other. An IndiGo spokesperson said no one was injured but four passengers complained of giddiness and two cabin crew needed first aid, due to the air turbulence, which took place around the same time. The incident happened yesterday, when Mumbai to Guwahati IndiGo plane (flight 6E-813) had to climb higher about 250-300 feet after experiencing turbulance due to monsoon activity over the sub-continent. At the same time, the other IndiGo plane to Chennai (flight 6E-136) was almost on the same path, following which, the two flights came close to mid-air collision situation but timely "technical intervention" helped the pilot of one of the aircraft to control the situation and prevent the possible disaster, sources said. After receiving an alert on Traffic Collision Avoidance System (TCAS), flight commander of one of the flights took "evasive action" to steer away the aircraft to a safer distance, they said. TCAS is onboard equipment that alerts pilots about the traffic in the proximity of the aircraft and also instructs them about the avoidance action (Resolution Advisory) to maintain desired separation between two aircraft. Due to the monsoon activity, passengers along with the cabin crew onboard were physically shaken, the spokesperson said. Source said the incident happened when the planes were over the Dhaka (Bangladesh) airspace as all aircraft to and from Guwahati fly through this airspace. Even though the incident happened in the Dhaka FIR (Flight Information Region), Airprox Investigation Board-to be set up by aviation regulator DGCA-would probe the incident. Airprox is a situation when two aircraft come dangerously close to each other. Following the prescribed protocol, the pilot immediately applied the Resolution Advisory (RA) triggered by TCAS (Traffic Collision Avoidance System), the spokesperson said.