On trains and planes, a summer of discontent is intensifying.

“Consider whether travel is necessary,” was the message from Northern, which runs trains in a large area of the country, from Newcastle and Carlisle in the north as far south as Liverpool and Lincolnshire.

RMT union members working for Northern are on their third and final day of strike, with fewer than half the normal schedule of trains operating.

“The majority of services today will run between 7am and 7pm, though many routes will start to wind down from late afternoon,” the train operator warned passengers.

The dispute is over plans to introduce driver-only operation on some routes. A similar dispute is affecting Merseyrail, where staff are taking industrial action today and on Sunday 23 July.

Five lines in Merseyside are closed completely, including Chester to Hooton and Liverpool to Kirkby. On the lines that are running services will end by about 7pm.

The train operator said: “The industrial action scheduled for Sunday 23 July coincides with the final day of The Open golf championship at Royal Birkdale.” It plans to issue a “revised” timetable for that day nearer the time.

Southern has been in dispute with both the RMT and the drivers’ union, ASLEF, for over a year on the same issue.

With drivers on the 13th day of an indefinite overtime ban, Southern was in the unusual position of not having to cancel any additional trains when members of the RMT working as guards went on strike today, “This is expected to have no further impact on services,” the train operator said.

The RMT has been taking industrial action for over a year against the extension of driver-only operation in the network from London to Surrey and Sussex. Suburban and main-line services have been

The union insists the dispute is not about pay or conditions but is down to concern over passenger safety.

Passengers using trains to and from Britain's busiest station, London Waterloo, faced a frustrating afternoon. A trespasser on the line between Putney and Mortlake was blamed for the cancellation or severe delay of dozens of trains. Commuters endured chaotic scenes, boarding one of the few trains to be running and then being told it was cancelled.

At Heathrow, British Airways Mixed Fleet cabin crew are on day 10 of a 16-day strike in a bitter dispute that began over pay but has broadened to include what the Unite union says are punitive sanctions on strikers.

Last week BA told non-striking cabin crew that they would be paid an extra £250 each, representing the bonuses that have not been paid to Mixed Fleet staff who have taken industrial action.

British Airways is cancelling around six long-haul flights each day. Around 30 short-haul flights have been operated by Qatar Airways, which has lent nine planes to the strike-hit carrier.