If 5G was using spectrum way outside the band that these altimeters are supposed to be using... then we wouldn't have this issue. Those 737s aren't new, they certainly had permission to use that spectrum for years and while they may have had years to fix their equipment, it's certainly not as trivial as "add a high pass filter".

Now, I do agree that this should have been caught 5-10 years ago, when the standard was being developed. Boeing's incompetence wouldn't surprise me, which is probably why we see "FAA says problems for Boeing in 5G" as the headline, instead of "Aircraft companies warn of interference in safety, navigation equipment, ask FCC to reconsider" as the headline, 5 years ago. Although, as noted in the article, it seems that the FAA has been warning about the conflict - I'm just surprised that the FCC would go ahead with 5G if they had been flagged early enough.

So here we are, the FCC, in its negligence, assigned conflicting portions of the spectrum, Boeing, in its incompetence, didn't catch it - and now it's a big mess.