The vessel, built at Ferguson Marine in Port Glasgow, left Troon at 6.30am on Monday bound for Brodick.
Launched in November 2017 and originally due for delivery in 2018, the ferry, and its sister ship Glen Rosa, have endured a saga of costly delays and technical problems at the Port Glasgow yard.
But after completing the first voyage on Sunday, CalMac said it had overcome some last-minute snags on the vessel.
MV Glen Sannox has finally entered service for CalMac. (Image: George Munro) However, part of the anchor system requires a replacement which is expected to arrive in early February.
There are also questions around whether its sister ship, the 3,000-tonne Glen Rosa, will face further delays to its handover to the government agency which owns the vessels.
The state-owned shipyard, Ferguson Marine, is conducting a “lessons-learned exercise” and is set to provide an estimated completion date.
Officials have previously said they are targeting a handover in September.
The Glen Sannox’s first voyages are nevertheless an important milestone in the procurement of the two ferries.
The cost of the two vessels is expected to be more than triple the original price tag of £97 million.
The Glen Sannox is in service at last – more than seven years after the vessel’s hull was launched at Ferguson Marine in Port Glasgow. (Image: Jane Barlow/PA Wire) During the test run on Sunday, with crossings between Troon and Brodick, Glen Sannox carried a maximum of 154 foot passengers, 53 cars and two commercial vehicles.
Duncan Mackison, chief executive of CalMac, said earlier: “Operating a test run with MV Glen Sannox gave the crew a fantastic opportunity to stress test the vessel and ensure the experience people have aboard is optimal before she formally enters service.
“A massive effort has gone into getting MV Glen Sannox to this stage, and everyone at CalMac is excited to have her in the fleet and serving Arran.”
Both the new ships are having to use Troon as their mainland port, rather than the normal Arran terminal at Ardrossan, because of essential upgrades required at the North Ayrshire port.
Agreement has yet to be reached between Ardrossan’s private owner, Peel Ports, North Ayrshire Council and Transport Scotland over financing of the upgrade work needed to accommodate the larger vessels.
The new vessel is unable to serve Ardrossan because essential upgrades required to accommodate the ship have yet to be carried out. (Image: Save Ardrossan Harbour) In addition, overhauls of other vessels in the CalMac network, along with major repair work needed on the usual Arran vessel, MV Caledonian Isles, mean there will be no sailings at all to or from Ardrossan until March 28.
Ahead of the first official sailing, Lib Dem MSP Willie Rennie said: “This must be Scotland’s most haunted ship: years late, millions of pounds overbudget, a fake launch and now last-minute glitches and even more delays to its sister ship.
“Islanders will need to see the Glen Sannox setting sail for themselves before they can believe it.
“After years of delays and excuses, island communities won’t forget the SNP’s neglect of them any time soon.”