United Technologies says Honeywell's offer was too low
United Technologies has said a $90.7bn (£65.4bn) purchase offer from Honeywell understates United Technologies' value.
United Technologies rejected the offer, which would have created one of the aerospace industry's largest companies.
In statement on Friday, chief executive officer Gregory Hayes said, "It would be irresponsible to move forward with the proposed combination."
Honeywell offered each United Technologies shareholder $108 in cash and stock for the company.
United Technologies said getting regulatory approval for the tie-up would be nearly impossible and the time spent applying for it would lower shareholder value.
Honeywell disagrees with this view. In a statement released on Wednesday, the company said, "We do not see the regulatory process as a material obstacle to a transaction."
The two companies have discussed merging before but concerns that the deal would be rejected by regulators have prevented them from moving forward. An offer from General Electric to buy United Technologies in 2000 was rejected by regulators.
If United Technologies and Honeywell combined, the new company would be responsible for most of the equipment on commercial airlines.