Around 600 passengers arrived at Amsterdam's Schiphol Airport on the two KLM flights on Friday and faced hours of delays and testing due to concerns over the new virus variant.
On the basis of initial testing, the Dutch health ministry estimated there may be around 85 positive cases among the passengers.
"Travellers with a positive test result will be placed in isolation at a hotel at or near Schiphol," health authorities said in a statement.
"Of the positive test results, we are researching as quickly as possible whether they are the new variant of concern, now named Omicron."
The Dutch government banned all air travel from southern Africa early on Friday.
Health Minister Hugo de Jonge said passengers already en route to the Netherlands would have to undergo testing and quarantine upon arrival.
A health authority official in Kennemerland, the Dutch region that oversees Schiphol, said the positive cases were being analysed to determine whether they are the new strain.
The Dutch government separately on Friday announced the night-time closure of bars, restaurants and most stores as it grapples with a record-breaking wave of COVID-19 cases that is swamping its healthcare system.
Law enforcement officials were preparing for possible unrest after a demonstration in The Hague on Friday to protest against the new measures.
