"The loss of Peter will be felt particularly keenly through our membership, particularly amongst pilot colleagues and those students he helped train at the Ardmore Flying School."
Pender described Callagher as a great leader.
"He was a pilot and colleague destined for great things."
He grew up surround by the aviation industry and his father Craig Callagher is an air traffic controller and also an NZALPA member.
The Transport Accident Investigation Commission and the Civil Aviation Authority are both investigating the crash.
Pender said he could not speculate on the cause while the investigations are underway.
NZALPA was assisting Ardmore support staff and student pilots.
"All over New Zealand, particularly throughout our close-knit aviation community, our thoughts are with Pete and Zak's family, friends and colleagues. It is truly a sad and reflective time for New Zealand Aviation."