Irish rider Seamus Greene remains in a 'critical' condition after crashing in Monday night's practice session at the Isle of Man TT.
Deaths are a regular occurrence at the Isle of Man TT
Donegal man Greene suffered head injuries after being involved in an accident with Japanese rider Jun Maeda.
The Japanese competitor sustained pelvic injuries with his condition described by race organisers as "serious", although he was conscious.
Both competitors were airlifted to hospital after the accident.
The riders were in collision coming out of the Union Mills section about four miles onto the circuit.
The practice session was halted after the accident although it resumed later in the evening.
A TT spokesman said: "There was a two-bike incident coming out of Union Mills on the way to Glen Vine section.
"The riders involved were Jun Maeda and Seamus Greene, who were in collision, and both have been taken to hospital by helicopter."
Honda rider John McGuinness was fastest in Saturday's practice
Monday's serious accident follows two other serious crashes in the Isle of Man over the weekend.
Sidecar racer Tony Smith and his passenger Barry Pepperrell were killed in a practice race for the Pre-TT Classic Road Races on Friday night.
This was followed on Saturday evening by a serious accident involving sidecar crew Doug Dano and James Cornell.
Dano is described as being "fairly comfortable" in the island's Nobles Hospital although his passenger remains "critical" after sustaining multiple injuries.
Martin Finnegan, on the Klaffi Honda Fireblade, was fastest in Monday's shortened practice session after registering a best lap time of 18 minutes and 38.32 seconds at an average speed of 121.457mph.
Guy Martin was second fastest, 4.17secs adrift, and Ian Lougher was third fastest though none could match the 18:33.23 benchmark set by John McGuinness on Saturday.
Martin was fastest in the Supersport class, but nevertheless slower than Ian Hutchison's Saturday standard, while Adrian Archibald led Monday's Superstock practice times though Bruce Anstey was faster on Saturday.