The M2 has reopened after three rush-hour crashes closed both carriageways, leading to severe delays.
A car heading towards the coast hit the central reservation at 06:50 BST. Five minutes later, two coast-bound trucks collided, Kent Police said.
Three vehicles crashed on the London-bound side 20 minutes later.
Both carriageways were closed between junctions five and six for Sittingbourne and Faversham, but have since reopened.
Police said a car travelling in the direction of the coast hit the central reservation. The driver suffered minor injuries.
When the two lorries - a Mitsubishi Fuso tipper truck and a DAF truck - crashed on the coast-bound carriageway, one of the lorry drivers suffered serious injuries.
Police said the 25-year-old man, who had been driving the Mitsubishi, was airlifted to a London hospital.
The two trucks had been approaching the scene of the earlier incident, a police spokesman said.
Three vehicles were later involved in the third crash on the London-bound carriageway but no injuries were reported.
Police, South East Coast Ambulance Service and the Kent Air Ambulance were called to the scene.