Ryanair and the UK’s largest airport group have announced that they have launched a legal challenge calling for transparency in the government’s handling of its contentious “traffic light” travel system. The move by Europe’s biggest airline and Manchester Airports Group (MAG), which also runs Stansted and East Midlands airports, is backed by several other major UK carriers. Ryanair and MAG argue that ministers have not been clear about how the government has made its decisions regarding the categorisation of countries as red, amber or green, undermining consumer confidence to book summer holidays. Court papers are due to be filed on Thursday with both health secretary Matt Hancock and transport secretary Grant Shapps named as defendants. MAG and Ryanair said the judicial review has been prompted by the lack of transparency in how the government made decisions in its first review of the traffic light lists which saw Portugal unexpectedly moved to amber earlier this month. They are calling on the government to publish the Covid-19 prevalence thresholds it deploys to determine whether destinations are classed as red, amber or green along with criteria, advice or information that informs its decision-making. Michael O’Leary, CEO of Ryanair Group, said: “The UK’s traffic light system has been a complete shambles from the beginning. “This go-stop-go-stop policy is causing untold damage to the aviation industry and frustrating and upsetting millions of British families when they see their holiday plans and family visits disrupted by the government’s mismanagement of international travel. “We call on prime minister Boris Johnson to explain the scientific basis behind this system that the government seem to make up as they go along and to establish a data-driven transparent model that could restore confidence in air travel ahead of the very crucial peak summer months.” Charlie Cornish, MAG’s chief executive, said: “The whole travel sector recognises the critical importance of protecting public health … That is why we originally welcomed the Global Travel Taskforce’s traffic light system, which the government said would be based on a ‘a clear and consistent evidence-based approach’.” He added: “Recent developments suggest that the government is now unwilling to open up international travel by putting low-risk countries on the green list. For most countries, the traffic light seems to be stuck on amber for no obvious reason, despite having prevalence rates much lower than the UK. “The government is not being open and we simply cannot understand how it is making decisions that are fundamental to our ability to plan, and to giving customers the confidence to book travel ahead. “These issues must be resolved urgently - and ahead of the review point later this month - to allow everyone to understand how the system operates, and to create the opportunity for international travel to resume to the fullest extent possible over the summer.” The Department of Health and Social Care and Department for Transport has been contacted for comment.