The first session for the event, which includes the Classic TT and Manx Grand Prix, opened with a speed-controlled lap for newcomers on the TT course.
Saiger's opening lap of 117.18mph on his Greenall Racing Kawasaki was the quickest of the evening session.
The second practice session will be held on Tuesday.
Monday's scheduled second qualifying session has been cancelled due to rain and low-lying mist on the Mountain.
Double Manx Grand Prix race winner Andrew Dudgeon was second fastest on the night with 115.39mph, with Australian David Johnson and Lee Johnston both averaging more than 114mph.
Fifteen-time TT winner Michael Dunlop missed the session to compete in the Ulster Rally, whilst Kiwi Bruce Anstey topped the Lightweight timesheets.
Thirty-eight Manx Grand Prix newcomers completed their compulsory speed-controlled lap under the guidance of experienced TT racers.
Santon-based Michael Evans topped the qualifying board on his Senior Martin Bullock Motorsport Suzuki with 114.518mph.
Meanwhile, Brendan Fargher (114.236) Tom Robinson (113.988) and Glenn Harrison (113.828) all posted competitive times on their 600 machines.
Six newcomers slid off on their opening laps with Lief Williams and David McConnachy taken by ambulance to Noble's for check-ups.
All have been reported as okay.
Austrian Horst Saiger has gone quickest in the opening practice session for the 2017 Festival of Motorcycling on Saturday.