Many native francophones I've spoken with, as well as various books, pronounce -ais and -ait as [ɛ]. My issue with this is that I don't hear people using it that way.
I hear aller /ale/ and allait /alɛ/ as almost indistinguishable from each other. Conversely, the end sound of allait /alɛ/ sounds extremely different from the vowel in être /ɛtʁ/ or tête despite supposedly sharing a sound.