What were the safety recommendations following the Aeroperú Flight 603 crash?
who was responsible for ATC relaying false altitude information to the pilots


Not an easy question mostly because it asks (even if not directly) to put the blame on someone. And although there is not an explicit rule for not doing this, I prefer avoiding it in respect to the dead and the ATCOs doing their job as good as they can.

I will focus on the reason behind the "false reports" and not the responsibilities. The RADAR system the ATCOs use relies on aircraft systems for two things: one is to identify the flight (Mode A) and the other is to get its altitude in hundreds of feet (Mode C).

Now if you recall what happened, the static ports were duct taped for some routine cleaning of the fuselage and were not removed. This affected the airplane's altitude indicator and consequently the altitude transmitted by Mode C.

So the ATCO was reporting back to the plane the same erroneous altitude the pilots were seeing in the cockpit.


  has anything changed since then to prevent that from happening again?


I don't know if there was any action taken after the accident but I think that there wasn't anyone needed: there is regulation (need to make some research to find it) which specifies that all "foreign" parts attached to a plane for protecting its vital parts should have a prominent red "REMOVE BEFORE FLIGHT" ribbon.

The duct tape was of silver non reflective color (if I recall correctly) and had no ribbons. When the crew inspected the plane at night with flashlights they couldn't spot them.