I have been making a future colonization scenario where people have vast colonies on Mars and cloud top bases on Venus. These things are unbelievably large. I've already thought of a way to travel between these on Mars, but Venus is another issue. Could you use a common passenger jet (most likely modified to use solar power, however) to traverse these large expanses of atmosphere? How about any other form of common air travel? Helicopters? Gliders?
While in theory the atmospheric pressures and temperatures in the upper regions of Venus' atmosphere are more conducive to the operation of aircraft, you still have a problem; sulphur dioxide. This is one of the emissions that grounds planes during volcanic eruptions meaning that even if you can fly the plane there, the maintenance costs are likely to be prohibitive.
That said, given the density and the nature of the gases in the Venusian atmosphere, you don't need aircraft to fly between bases. You could literally float.
The idea behind the cloud cities of Venus is that molecular oxygen, nitrogen and other gases that humans need for a healthy life, particularly at the temperatures we operate at, would actually float in the atmosphere at a particular altitude because the density of the super heated CO2 is sufficient to support it. So, you basically can build a lightweight 'bubble' of the gases we breathe and put a city on the floor of it and it would float around Venus. Obviously this is a simplification, but it's functionally correct.
The point being, you could do the same thing with your aircraft or transport vehicles. Basically create a series of mobile bubbles, fill them with breatheable air, give them propellers and the like to move about, and you've literally got an airship in which the crew, passengers and goods can all safely reside in the air envelope - you don't need hydrogen or helium to make the craft lighter, because in that environment normal air is already lighter.
This would actually be a failsafe for all but catastrophic breaches of the air envelope because even if you run out of power, you float until someone picks you up or tows you in.
The other advantage of this of course is that your airships are likely to be capable of moving larger cargoes and passenger lists than a conventional 747. They would be more like the trains of the Venusian sky.
Obvious problem number 1: there's no free oxygen in Venus' atmosphere, so you can't run any kind of combustion engine. Lets assume you're using some other kind of engine though, though I won't specify which.
Venus at low altitude is very, very hot and has very high air pressure. Your aircraft would disintegrate in short order. Once you get to an altitude of 50km though, atmospheric pressure is nearly the same as that found on the surface of Earth... about 1.07 atmospheres, though it is a little warm at 75 degrees C. Go a few kilometres higher and you'll get half an atmosphere of pressure and a balmy 27 degrees air temperature. At 60km conditions start to look a little more like they would for a Boeing 747 at cruising altitude on earth, though quite a lot warmer.
You'd still have to contend with a possibly very corrosive atmosphere though... there's quite a lot of sulphuric acid in Venus' atmosphere, but if you avoid clouds you might be OK but it would be best to thoroughly corrosion-proof everything. Wind speeds are quite strong up there too, but windspeeds at high altitude on Earth can also be pretty brisk and that hasn't stopped commercial flights being entirely practical and largely safe.
Any form of flight that would work on earth and not need oxygen for the engines to work should function just fine.
I'm not sure a solar powered passenger jet would work, though... I'm not about to run the numbers myself, but I think the available surface area is too low to provide the same amount of power those four big gas turbines would on Earth, and even at 60km altitude there can be thick cloud cover. If you don't have compact and lightweight fusion power, you'll have to scale back the cruising speeds of your aircraft somewhat. Maybe electric props or fans with fuel cells as the power source might work. At 50km you can make bouyant balloons filled with human-breathable gas, so as long as you have some good air conditioning maybe zeppelins would work for you...
In a direct answer to your question no you could not use a common passenger jet unmodified.
Firstly the atmosphere would contain a lot of sulphur dioxide and a small amount of water creating sulphuric acid which would rapidly corrode the structure of the jet. That said a jet could reasonably easily be modified to incorporate plastic coatings such as polytetrafluorethylene to resolve that issue. But a bigger issue would be propulsion. How would the structure be moved in the atmosphere as no oxygen is present for combustion?
At the altitude the cloud cities would be situated the atmospheric density is similar to that at ground level, or ,say, the troposphere, the lack of oxygen knocks out any possible jet aircraft.
While solar-powered aircraft can be possible. They will be too light and too fragile. This is a major potential problem. Remember the Hellish abyss of the Venusian atmosphere lies down below.
The most probable aircraft for travelling between cloud cities will be nuclear-electric powered helicopters or propeller-driven fixed wing aircraft. Pressurization and airtight compartments will be an absolutely necessary to ensure they can breath air containing oxygen. This will keep out the sulphuric acid in the clouds and aircraft will have be acid-proof.
Not totally infeasible, But Boeing 747's cruising Venusian skies, definitely not. Jets are also definitely out. But propeller or rotor aircraft with suitable power sources, presumably nuclear instead of solar, are quite feasible.