Aircraft usually relay data about temperature and wind speed in the upper atmosphere to meteorological agencies world over. This data is used in the forecasting models which provide you with the near-term weather forecast, such as one or two days out. The data, which is imperative for accurate predictions of weather, has been unavailable to the Indian Meteorological Department since a majority of flights are out of operations due to the nationwide lockdown, coupled with staff constraints.

As a backup, IMD had moved back to their traditional statistical forecasts which are built on the basis of historical data. However, weather data generated by aircraft is also useful for generating predictions about thunderstorms and temperature swings. With flights closing out, it has become largely impossible to capture such data and patterns over a period of time, causing a gap in the model that analyses trends.

Now, IndiGo has collaborated with the IMD to provide crucial aircraft data on wind, humidity and temperature relayed by the aircraft sensors. IndiGo has incorporated a plan for its pilots to report high-level wind and temperatures at different stages of a flight as desired by IMD across all flight operations. The pilot reports will capture and share observations at cruising altitude MIDWAY of the destination, at cruising altitude just before the start of the descent, near FL100, near FL050 and position in coordinates within 2HRS of observation to support the Wx forecast model.

As per Captain Ashim Mittra, who is the SVP of Flight Operations at IndiGo,

As part of this initiative, we have made pilot reporting compulsory on our flight operations. We will ensure to share observations from every flight within 2 hours to the IMD headquarters, so that they can use this data for the benefit of the nation.

I am not sure which airline has been helping IMD with the data so far and could not find it on their website as well. My guess is it was optional so far to share data with the IMD, and now IndiGo is making it compulsory for their pilots to get this done, which was an optional earlier.