I think we're still puzzling it out, as there's both radiative forcing and contrails (the vapor, or condensation trails planes emit).

If you check out these two emission factors from the UK government, one taking radiative forcing and contrails into effect and one not:

https://www.climatiq.io/explorer/emission-factor/domestic-fl...

https://www.climatiq.io/explorer/emission-factor/domestic-fl...

You'll see a noticeable difference, (almost a doubling)

Full disclaimer: Work at Climatiq, but the emission factors are not from us directly.