[p_l]

Possibility of bit flips from cosmic radiation only really came to fore in 1990s, and some aircraft and parts predate that.

[15155]

Smaller semiconductor feature size greatly increases the likelihood of these types of errors.

[p_l]

For a long time ECC brought most of effect as hedge against failing silicon, and local EMI. Aviation had benefit of careful EMI designs and appropriately selected chips, so it was seen less of a benefit...