Are airliners sensors used to feed weather prediction models?
Indeed, airlines are equipped to measure atmospheric data and then put into weather models. The WorldMeteorological Organization's program is called AMDAR. Several articles highlight the impact that the lack of flights have had on the initialization of weather models.

https://www.npr.org/sections/coronavirus-live-updates/2020/04/03/826848818/one-more-coronavirus-problem-accurate-weather-forecasts

https://www.boston25news.com/news/local/covid-19-forecast-how-grounded-flights-are-impacting-weather-forecasting-data/RB7HY6G5ONGE3EHROUKSKT4SB4/

There are a few papers that explore the impact that aircraft data has on initialization:
https://journals.ametsoc.org/doi/full/10.1175/MWR-D-17-0380.1
https://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-14-00055.1
https://journals.ametsoc.org/doi/pdf/10.1175/2009WAF2222321.1