The phrase "major gaps remain" is grammatically correct and can be used in written English.
You can use this phrase to indicate that there are significant issues or uncertainties that still need to be addressed or resolved. It is often used in discussions or reports where there are still significant challenges or obstacles that need to be overcome. Example: "Despite significant progress, major gaps remain in our understanding of the causes and possible treatments for this disease."
B7 SECURITY GAPS -- Experts warn that major gaps remain in aviation security nearly two months after the terror attacks.
[A1.] Air Travel Security Gaps Persist Major gaps remain in aviation security nearly two months after the terrorist attacks.
Major gaps remain in our knowledge of the potential ability of domesticated animals to contract or spread these zoonoses.
Some major gaps remain in the authorities' knowledge of Mr. Nichols's movements after he fled the Fulton County Courthouse on Friday.
Still, major gaps remain in identifying, aggregating and responding to calls for rescue and ongoing resource needs, like food, water and shelter.
We're making significant progress, yet major gaps remain.
With Congress in a stalemate over whether to federalize airport screening workers, experts warned yesterday that major gaps remained in aviation security nearly two months after the terrorist attacks.
Despite the recent progress in gasoline surrogate fuel combustion research, there are still major gaps remaining; these are critically discussed, as well as their implications on fuel formulation and engine design.
The evaluation found that more RH services were available than a decade earlier, although major gaps remained in most of the technical areas, with gender-based violence as the least developed technical area.
However, major knowledge gaps remain in our understanding of how TLRs regulate the development and persistence of T- and B-cell memory.
Major knowledge gaps remain in the processes of erosion via plucking of bedrock blocks where joints are not river-bed parallel; waterfall erosion by toppling and plunge-pool erosion; feedbacks between weathering and physical erosion; erosional bedforms; and morphodynamic feedbacks between channel form and erosion rates.
