The contracting-to-facilities management business stunned the construction sector last week with its largest-ever takeover bid. Servisair, the £162m-turnover baggage-handling specialist, responded by attacking Amey's bid as "wholly inadequate".
Amey now faces a two-week wait to see whether other bids emerge.
On Monday, Ashley said: "We think we've made a fulsome offer. There are plenty of rumours about other bidders, but no one has emerged so far." He refused to rule out an increase on Amey's offer should a bidding war erupt.
Amey launched its hostile bid for Servisair after takeover talks failed to progress. Ashley said Amey felt compelled to make a unilateral approach of 200p a share after Servisair's shares rocketed from 102p when talks began in December to 176.5p by 21 January.
Ashley said this bid was within Amey's capabilities. The deal for £81.5m is a little under half of Amey's market capitalisation.
He added: "I wouldn't say it is an ambitious move. It's a natural progression. We're into roads, we're into rail – why not aviation?" Amey has offered the full bid amount in cash to Servisair's shareholders. Ashley said Amey had "northwards of £40m" in the bank at present, with the £40m balance to be raised from borrowings.
Ashley said the move reflected Amey's ambitions in the services sectors. It has been moving away from its core construction business towards FM-based work, with 85% of its profit now coming from services. He added, however, that Amey had no plans to sell its construction business.
The takeover got the thumbs-down from investors. Amey's share price dropped 47.5p in the two days following the announcement.
Leslie Kent, construction analyst at stockbroker Townsley, said: "I'm all in favour of diversification. But this is a very large fish for Amey to swallow. As yet, Amey's skills in aviation are unproven. If it goes wrong, it could go wrong in spades."