Operating around the clock, the 343 Bus Éireann route from Limerick Bus Station to the airport will run every 20 minutes during peak hours and every 30 minutes during off-peak hours on weekdays.
Hourly service will be available from midnight until four in the morning.
The alterations will take effect on August 25, Sunday.
"100% of timetabled services" will employ fully accessible buses with low floor access, according to Bus Éireann and the NTA.
The 316 and 317 routes that link to Sixmilebridge, as well as the 330 route to Ennis and Newmarket-on-Fergus, will all be improved, according to the NTA.
"Bus Éireann is delighted to introduce these improved services between Limerick, Shannon and Ennis, significantly increasing transport options for passengers," Stephen Kent, CEO of Bus Éireann, stated.
Anne Graham, chief executive of the NTA, stated that the "revised network will operate at a higher frequency which will benefit communities across the region who want to use public transport to get to work, school or attend leisure activities in the area" .
Niall Kearns, Airport Director of The Shannon Airport Group, has also praised the adjustment.