Kent Police is appealing for information following a "serious" crash on the A2 near Dartford yesterday.
A 63-year-old man from Medway and the 60-year-old female pillion passenger came off a black Triumph Thunderbird 900 on the London-bound carriageway, near the slip road for Bean at 12.30pm.
Both casualties were airlifted to hospital following the accident.
The man was taken to Kings College Hospital with injuries described as "serious" and the woman was taken to St George’s Hospital in Tooting, London.
Both of them remain in hospital in a serious but stable condition.
The road was closed until about 4pm while officers from the Serious Collision Investigation Unit investigated the incident.
Sergeant Chris Wade, of Kent Police’s Serious Collision Investigation Unit, said: ‘We are investigating a single vehicle collision involving a motorcycle.
"I would ask anyone who witnessed the incident, but were unable to stop at the scene to speak to police, to contact us.
"I would also encourage anyone who might have seen this vehicle prior to the collision to call police.’ Do you have information?
Witnesses or anyone with information is asked to contact Sergeant Chris Wade at Kent Police by calling 01622 798538.