The phrase "a major ongoing" is correct and usable in written English.
It can be used to describe something significant that is currently in progress or continuing over time.
Example: "The company is facing a major ongoing challenge in adapting to new market trends."
Alternatives: "a significant continuous" or "a substantial ongoing".
The issue of cheating in sports is a major, ongoing problem".
Frozen or faulty sensors are a major ongoing issue in air safety".
Real-time water management is a major ongoing challenge for PEM fuel cell technologies.
The development of communication standards in healthcare is a major ongoing engineering effort.
Complaints by parent, teacher, and religious groups that network television was no longer appropriate for family viewing became a major ongoing refrain in the 1990s.
Their retirements are steps in the wholesale shuffling of positions that will be revealed in the weeks ahead, party insiders said, and do not signify a major ongoing power struggle.
By S&P definition, that means a sovereign faces "major ongoing uncertainties and exposure to adverse business, financial, or economic conditions which could lead to the obligor's inadequate capacity to meet its financial commitments".
This article provides a brief overview on major ongoing activities on glacier, snow and related runoff research in order to then analyze data gaps and research needs from a climate change adaptation perspective.
And in another major ongoing case, a professor at Marquette University is facing termination for publicly criticizing a graduate student instructor who told a student not to oppose same-sex marriage in a philosophy class discussion.
Two years ago, Natalie James, the Fair Work Ombudsman, said "achieving widespread employer compliance with minimum employment standards is a major and ongoing challenge in Australia".
