You can book your flight on iberia.com and hold the price 72 hours without a commitment to buy the ticket.

You will pay for this service when you make the booking but it will be deducted from the final price of the ticket . The cost will depend on the length of the flight:

Once you have made up your mind, just go to Booking management and complete your purchase within 72 hours or the booking will automatically be cancelled and you will lose the amount already paid.

Use it in countries where it is available, provided you make the booking at least 5 days before the departure of the flight.
You can hold the booking for 72 hours on Iberia flights (operated by Iberia, Iberia Express or Air Nostrum) and on codeshare flights with British Airways, or when the booking includes flights by both airlines.
In certain other countries the purchase terms and conditions do not permit the automatic issue of tickets. In these cases, follow the instructions indicated during the purchasing process.