Re: Obviously not GPS jamming
INS/IRS do drift, which is why modern aircraft don't rely on them entirely. The INS/IRS positions are compared regularly with DME/GPS fixing (and radar fixes on older military aircraft) to compute an accurate position. using Kalmann filtering techniques.
Something like a 146/V-bomber would have been much more prone to errors, since the computation was minimal/non-existent.
Biting the hand that feeds IT
