The IAG-owner carrier will reduce flight operations by around 6% by removing "lower margin flying" and stripping out "poor performing routes".
It is also aiming to cut head office employee costs by a quarter. Its stated aim is to "achieve and sustain" a 12-15% operating margin.
Network changes will begin in late September and continue into summer 2027, affecting both long- and short-haul flying.
As a result, two A330 aircraft and four A320 aircraft will be taken out of service next summer. Four routes will be cut entirely, and another four moved to summer-only operation.
Aer Lingus cited several "wider challenges" for the efficiencies, including the "continued challenging macro-economic environment" and a 45% increase in competing capacity on transatlantic routes last winter (2025/26).
In addition, it said increasing seasonality, higher fuel, supplier and carbon costs, and a €103 million first quarter loss, all contributed to the proposed changes.
Aer Lingus will consult with employees and unions over the head office cuts and network changes, warning up to 500 employees could leave the airline. It follows an earlier 25% reduction in senior management roles.
Chief Executive Lynne Embleton said “Our accelerated transformation aims to set Aer Lingus up for the future; to ensure the airline is a strong investment case and able to weather the turbulence in our industry.
"An efficient cost base, coupled with investment in our customer experience will enable Aer Lingus to fulfil its ambition to be the airline of choice connecting Europe with North America, support future growth and continue to provide connectivity and significant economic contribution to Ireland."
Across its long-haul network, Aer Lingus will axe its Dublin-Denver service from 28 September, its Dublin-Minneapolis service from 24 October and its Dublin-Las Vegas service from 3 December. Its Dublin-Seattle service will move to summer-only operation from 24 October.
Short-haul changes include discontinuing its Dublin-Split route from 29 September, and move its Frankfurt, Hamburg and Malta routes to summer-only from early November.
Customers affected by the network changes are being contacted directly and provided with reaccommodation or refund options.
Planned investments, meanwhile, include retrofitting 10 Airbus A330 aircraft cabins next year to introduce premium economy. This follows the rollout of Starlink WiFi across its fleet.