This unavailability is mentioned on their site [broken link removed]:
'A way to bank free of maintenance and transaction fees
You could have the opportunity to qualify for banking free of maintenance and transaction fees on your Personal Current Account when you register for AIB Phone & Internet Banking and have an AIB Debit Card. All you need to do each fee quarter is to make a purchase with your AIB Debit Card AND use AIB Phone & Internet Banking to make a debit transaction like paying a bill. Please refer to our Related Information section for further details. Other charges still apply. Please see our booklet [broken link removed]. This offer is available until further notice.
AIB Internet Banking customers may also access their accounts at any time by phone by calling AIB Phone Banking on 0818 724 724 or +353 1 771 2424 (from outside Republic of Ireland). This helps to ensure that, should you not have access to the Internet, you can always access our banking services.
Please note that AIB Internet Banking is not available for short periods typically commencing 3 a.m. (Irish Standard Time) Monday to Friday. In such circumstances, or if technical problems should occur, customers are directed to the telephone channel and these contact numbers are prominently displayed'