Collver alerted the crew that a satellite image had picked up "something" near the area where the submarine last reported its position, according to a Reuters witness aboard the flight on Wednesday.
The agonising wait for news of the whereabouts of the ARA San Juan has intensified in recent days as fears grow that the oxygen supply on board could be running low.
The submarine was en route from Ushuaia, the southernmost city in the world, to Mar del Plata when it reported an electrical malfunction shortly before disappearing last week.
"It's great to be able to utilize everything we have - all the training we have, the equipment we have - in order to come down here to Argentina to help find this submarine", said mission commander Lieutenant Zachary Collver, a 32-year-old pilot from Washington state.
According to Balbi, the event was "consistent with an explosion" and occurred in the area in which contact with the vessel was lost.
It's called the Comprehensive Nuclear Test-Ban Treaty Organisation, and one of its jobs is to scan the globe for signs of explosions.
"They did not tell us that they are dead, but this is a logical assumption", she said Thursday.
Argentinian Navy spokesman Enrique Balbi said the finding was important.
Relatives of crew express their grief outside Argentina's Navy base in Mar del Plata, on the Atlantic coast south of Buenos Aires, on Friday.
But family members said authorities were concealing the reality of what happened.
Speaking at a forum on open government in Buenos Aires, Argentine President Mauricio Macri said: "In these hard hours, I did not want to start without sending once again all my support to the families of the crew of the ARA San Juan submarine".
"We don't have any saint left to pray to; we have no one left to ask".
"I feel a lot of pain because of the decisions that were taken", said Elena Alfaro, sister of a crew member. "And today it was confirmed to me".
"Until we find the submarine and have all the information", Macri said on Friday, "we are not going to speculate on who is at fault".
The Argentine military submarine ARA San Juan and crew are seen leaving the port of Buenos Aires, Argentina June 2, 2014. It joins HMS Protector, a Royal Navy ice patrol ship; the HMS Clyde, an offshore patrol vessel; and an RAF C-130 in the search.
Russia's defence ministry has sent an oceanographic research ship equipped with two self-propelled deep submergence vehicles allowing it to examine underwater areas up to 3.75 miles below the surface.
Navy ships are searching the area, with the help of USA and Brazilian air forces.