Hi Blue Sky

Introduction

Your intro wanders around the main point, but it doesn’t get to the topic until the final word (‘enviroment’). You need to avoid wasting time and get to the point quickly, otherwise you will lose marks. See the official descriptors for IELTS Task 2 Writing (public version) here, under Task Response:

• Band 5: addresses the task only partially; expresses a position but the development is not always clear
• Band 4:  responds to the task only in a minimal way

You also have a fragment in your introduction (“While others have reverse opinion”) Read more about Fragments. This is a memorized phrase AND it’s not correct -  an article is missing. Here’s one possible rewrite of the intro:

Cheap flights today allow millions of travel for work or business. However, as air travel causes pollution, some people have suggested increasing the cost to reduce the number of travelers and protect the environment. In this essay, I will explain why…

Word Choice/Word Form/Usage

• There are many people believe that cheap air travels are a good option → There are many people who believe that cheap air travels are a good option  OR Many people believe that cheap air travels are a good option.
• In addition, many people whose their works depend on travelling are always avoid… → In addition, many people whose work depends on travelling avoid…
• The carbon emission of the old airplane engines usually discharged to the air. → The carbon emission of the old airplane engines is usually discharged to the air.

Shorten/Simplify

Try to replace nouns with verbs. You wrote:

Thirdly, cheap travels could be a good factor of employments increment.

Here's a suggested rewrite:

Thirdly cheap flights could also increase employment.

• The carbon emission of the old airplane engines usually discharged to the air. → Old airplane engines release/emit/produce a lot of carbon.

Ideas

The biggest problem with this essay is ideas. You need to really focus on the main ideas. This is simply not a convincing idea:

Moreover, old airplane shapes disfigure the aesthetic scene of the modern airport. For example, most of Kish airlines’ airplanes are old and negatively affect Dubai Airport shape.  In addition, the old airplanes have unpleasant effect on travelers’ feeling especially when an old one parks nearby a brand new one

The environment suffers from many problems, but the relative ugliness of old or new planes is not one of them. Some people love old planes! However, some old planes, like the ones in Kish Air’s fleet have much higher running costs. Keep to the topic: you are getting “tangential” now (see the official descriptors for IELTS Task 2 Writing (public version) here, under Task Response in Band 4).

Off-topic/Tangential

The rest of Paragraph 3 is definitely tangential, if not off-topic.  Yes, a plane crash is bad for the environment, but many cheap carriers (Ryanair, Air Asia) have relatively new planes, so focusing on Kish Air or on crashes is tangential. Do we ban cars because of the impact of car accidents on the environment? Planes are infinitely safer

Apart from the direct impact of plane emissions on the environment, what about the effect of those millions of tourists? The endless airport infrastructure and highway development? The noise pollution? The keyword is ‘environment’ and you need to focus on the main aspects.

Your conclusion mentions paint. I won’t even go there.

Just to put it in context, here is the number of fatalities on planes in the last 12 years. Last year, there were 33,800 deaths in car accidents in the US, and 2,200 in the UK. In one year. Perhaps we need to paint our cars different colors.