There may be a wide choice of fares on offer for a traveler sitting in the Economy cabin. For a start, there will be a flexible Economy fare, plus a variety of cheaper options called "discounted excursion fares".

Take a look at the Economy cabin below where 6 people are sitting in Rows 32-34 on a flight from London, UK to Chicago, USA. They started their trips in London and are all paying different return fares.

• £418.00:  Booked 21 days. Minimum stay 7 days. Maximum stay 1 month - London to Chicago flight was on a Wednesday.

• £448.00:  Booked 21 days. Minimum stay 7 days. Maximum stay 1 month - London to Chicago flight was on a Saturday.

• £503.00:  Booked 7 days. Minimum stay a Saturday night. Maximum stay 2 months - London to Chicago flight was on a Friday.

• £527.00:  Booked 7 days. Minimum stay a Saturday night. Maximum stay 6 months - London to Chicago flight was on a Tuesday.

• £557.00:  Booked 7 days. Minimum stay a Saturday night. Maximum stay 6 months - London to Chicago flight was on a Sunday.

• £1036.00:   A Fully Flexible Fare - Booked the day before flying. No minimum stay. Maximum stay 1 year - fare same whatever day of the week.

Help?

Don't worry. When you book a flight you know the date you want to depart and the date you want to return. The travel agent, air reservations clerk or internet site will find the price that matches your travel dates.

The next few pages show HOW those prices vary. If you understand some of the terms like "maximum stay" and "Sunday rule" you will find it easier to find the best fares and understand when changes to bookings can be made.