A full scale tourist invasion of Cuba from the US now looks inevitable - but the timescale remains doubt. The two countries this week agreed a bilateral air treaty enabling the establishment of scheduled flights. Since the initial thaw in relations only charters have been permitted. American Airlines, United Airlines and JetBlue were among the first to say they would seek early approval to start services. But under US law, Americans may only visit Cuba if the purpose of their trips falls into one of a dozen strict categories, including official Government or inter-governmental business, education and some exports and imports. Ordinary American tourists are still barred from travelling there. My advice to anyone toying with the idea of a trip from the UK is to go soon, before the atmosphere changes significantly - and before prices are pushed up significantly. But don't panic. It's unlikely there will be any flood tide of new scheduled flights, for the simple reason that Cuba doesn't have infrastructure adequate to cope. Airports will certainly need upgrading, not least to speed up baggage delivery and render those other than Havana's capable of handling big increases in passenger traffic. According to the authoritative magazine Air Transport World, IATA (International Air Transport Association), has offered the Cuban government expert assistance to head off mistakes. And the national airline Cubana will face challenges. At present it can only operate aircraft with a maximum 10% US-made content. That means it's largely limited to Russian built airliners. The timetable may also be affected by the result of the forthcoming US presidential election. It's surely open to question whether a right wing Republican winner would be keen to proceed at the same pace as President Obama. But however long it takes the inevitable outcome of this week's agreement will be make Cuba less distinct than other Caribbean destinations.