TEL AVIV — Local leaders often take visitors to Jewish settlements occupying the high ground of the northern West Bank to lookout points from where, on a clear day, they can see the glass towers of Tel Aviv, the shimmering waters of the Mediterranean and the contours of Israel’s heavily populated coastal plain.

The aim is to underline the strategic dangers that the leaders say would be inherent in any Israeli withdrawal from the area to make way for a Palestinian state.

In an effort to illustrate the other side of the argument, Peace Now, the leftist Israeli group that advocates a two-state solution and monitors settlement activity, took a planeload of Israeli members of Parliament, reporters and photographers on an aerial tour of the northern West Bank on Monday.

The group’s goal was to give a bird’s-eye view of the growth of the settlements and outposts across the hilltops, and to argue that if the settlements do not stop spreading, the land between the Jordan River and the sea will soon become indivisible for all practical purposes, and the two-state option will cease to exist.

“The point,” Peace Now’s secretary general, Yariv Oppenheimer, said over the plane’s public address system, “is to see how the reality has changed and how the binational state is getting closer.”

Israelis remain deeply split on the settlement issue. Although most polls indicate that a majority believe a two-state solution is the only way to guarantee Israel’s continuation as a state with a strong Jewish majority, many also feel a religious or emotional attachment to the West Bank as the country’s biblical heartland.

Israel’s partial moratorium on the building of new settler homes is scheduled to end on Sunday, which would pose a serious threat to the fledgling Israeli-Palestinian peace talks. With the Palestinians warning that a resumption of construction will spell the end of the negotiations, the looming deadline seems to have concentrated minds on all sides.

Peace Now used to use small planes that flew low over the West Bank for research purposes, but citing security reasons, the Israeli authorities no longer allow civilian planes or helicopters to fly low over the area. So the passenger jet used by the group took off at midday from Sde Dov, a small airfield on the Tel Aviv shore. Within minutes, it had crossed Israel’s so-called narrow waist and was flying over the West Bank territory that Israel captured from Jordan in the 1967 war.

The scenery was breathtaking even from 8,000 feet, with rolling terraced hills on one side, and the beige landscape of the Jordan Valley on the other.

Between the sprawling Palestinian towns and villages, the settlements, which are considered by much of the world to be a violation of international law, stood out distinctively, neat rows of red-roofed houses often built in concentric circles embracing the hilltops.

Several settlements, like Shiloh and Beit El, were named after biblical landmarks. Many have expanded onto nearby hills, with rows or small knots of mobile homes making up new outposts that are illegal by Israeli standards. Some 300,000 Israelis now live in the West Bank, about 11 percent of the population there, according to Peace Now.

In an effort to present an alternative to the two-state solution, some right-wing Israeli officials and commentators have offered vague notions of a peace based on Israeli-Palestinian coexistence in some kind of single-state arrangement, relying on findings by an Israeli researcher who says there are fewer Palestinians in the West Bank than commonly thought. Others on the right insist that the Palestinian state should be established in Jordan. Neither idea has any broad Israeli support.

It is clear from the air that empty sections of land remain on the West Bank, offering potential for much more building. The question is for whom.

Huge chunks of earth are being moved on one hilltop north of the Palestinian city of Ramallah, where the Palestinians are building their first planned city, Rawabi. But there is still no Israeli approval for a direct access road.

One of the less predictable Parliament members on the Peace Now flight was Arieh Eldad of the National Union, a far-right opposition party.

“It is always good and it warms my heart to see from every angle Jews living in every corner of the land of Israel,” he said.

The acclaimed Israeli playwright and director Joshua Sobol also joined the flight, weeks after signing a theater artists’ letter containing a pledge not to perform in a new theater in the settlement of Ariel.

He said the flight was like an M.R.I., and the results as seen through the window were “frightening.”

“The sickness,” Mr. Sobol said, referring to the settlements, “is spreading and metastasizing.”

After zigzagging back and forth across the West Bank, the plane landed back at Sde Dov in less than an hour, the short distances attesting to the apparent dangers in both dividing — and not dividing — the land.