When political conditions permitted, Jews from all over the known world used to find ways of getting to Jerusalem. The journey sometimes took months and many who embarked on it never returned.

Nowadays, miraculously, the journey to Israel at festival times is so much simpler and it has become a phenomenon.

In Europe, from St Moritz to Benidorm, kosher le Pesach hotels will attract thousands. With more money spread more widely across the Jewish spectrum than ever before, a significant number of Jews make a very good year-round living just catering to the Pesach trade alone.

The three pilgrim festivals were opportunities for Jews to come together and reactivate their sense of community.

The Hebrew term for these festivals is the Shalosh Regalim. The word regel, in Hebrew, means leg, occasion and people ("how can I feed 600,000 ragli?" says Moses).

Migration and pilgrimage both come under the rubric of regel. Of course the primary function was religious, spiritual regeneration, reconnection with community, and a return to one's teachers and rabbis. But there were other side benefits.

More controversially, regel and yerech (meaning "thigh") are Biblical euphemisms for sex. It may be no coincidence that the Talmud mentions the huge singles events that used to take place in Jerusalem at Tu b'Av and Yom Kippur.

Nowadays they happen at Succot and Pesach time. The modern massive singles gatherings in Jerusalem at festival time are most appropriate and continue an ancient tradition.

After all, procreation is our future and helping people get married is a primary obligation that guarantees plenty of reward in the world to come.

But there are few things I dislike more than huge, public communal sedarim. They are chaotic maelstroms where no one can make himself heard above the noise, and anyway everyone wants to get to the food as soon as possible.

Even where hotels offer private sedarim, tens of them compete for attention and service and no one is completely satisfied.

The only ones who are, are the housewives mercifully freed from the frenzied strains of housework and catering that make their life hell while the males sit back and enjoy.

A good home seder, where everyone is helping and joining in, is an experience impossible to recreate in hotels and it is sad that so many people nowadays substitute institutional pre-packed Judaism for the real thing.

But I am no killjoy and there is a lot to be said for vacations, even religious ones.

But there are dangers. Once, travelling was by foot - human or animal. It was dangerous and one made blessings when one set out, to thank God for one's safe arrival and safe return. Now most of us will travel by plane.

We have an ancient prayer Tefilat HaDerech (the prayer on embarking on a journey), whose text was written at a time when robbers and wild animals were a serious threat to travellers. We might need to update this to include missiles, technical failure, delays and viruses.

Similarly, some question how valid it is to make the blessing HaGomel thanking God for returning us safely home after a plane journey, when statistically it is safer than travel by car.

But I would argue that apart from leaving our wild animals off the London-Jerusalem route, we should indeed express our gratitude every time we return home.

It is not just the chances of being attacked by louts and thugs, or mown down by drunken drivers or people texting instead of concentrating on the road. Neither is it the increasing possibility that another Muslim fanatic will try to blow himself or herself and us up on a jet or with one.

The real dangers are much more mundane.

It is infection I worry about! We have just come through one serious flu scare. Without doubt, there are more on the way. Airlines recycle the same stale air and its germs.

Passengers bring all sorts of infections on board. You never know who or what has been on your seat and armrests. Most people do not wash their hands after going to the toilet.

So in addition to deep vein thrombosis, noisy, clumsy and inconsiderate co-passengers, crying, vomiting, and irritating kids, beware of the air.

These are the by-products of a modern society and technological advances. They only go to show how when one danger subsides another emerges.

So keep up with the blessings. There is no guarantee they help, but they certainly won't harm.

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