Go through your results for flights to Burlington Iowa in USA with Netflights. Although Aer Lingus usually has the best prices, it's best to double check what's available for your travel dates.
If these flights are too expensive, try searching for a different time of year. So if your dates are flexible, consider looking at different times of year.
Look out for flights with Aer Lingus, as they often have good deals. Or broaden your search by looking at other airports in USA.
You can also broaden your search by looking at more than one departure airport. Have a look around – you might be able to save by flying from a different airport or city.