Pope Francis speaks to journalists on his flight from Philadelphia to Rome Sept. 27, 2015. (Alan Holdren/CNA)

VATICAN CITY (CNA/EWTN News) - Pope Francis told journalists on board his flight to Rome that giving communion to divorced and remarried Catholics is a "simplistic" solution to the issue, and stressed that there are also other problems that need to be discussed.

"(It) seems a bit simplistic to me to say that the synod, that the solution for these people is that they can receive communion. That's not the only solution (asked for)."

What the "Instrumentum laboris" proposes "is a lot," he said. "Also, the problem of the new unions of divorcees isn't the only problem."

"In the instrumentum laboris, there are many (problems to be addressed). For example, young people don't get married. They don't want to get married. It's a pastoral problem for the Church. Another problem: the effective maturity for a marriage. Another problem: faith."

Pope Francis spoke to journalists on board his American Airlines flight from Philadelphia to Rome after spending 10 days in Cuba and the United States.

In the 47 minute inflight news conference, Francis answered 11 questions on themes such as his impressions of the United States after completing his first visit, bishop's accountability in cases of clerical sex abuse and the right of government employees to exercise conscientious objection as a human right.

The Pope's comments on divorced and remarried were the answer to a question posed by journalist Jean Marie Guenois of French news agency Le Figaro.

Guenois asked the Pope whether he is looking for a solution to the situation of divorced and remarried Catholics, as well as his response to fears that his recent 'motu proprio' on streamlining marriage annulments have created a de-facto "Catholic divorce," and whether they have closed discussion on the topic.

In his response, Francis stressed that with his motu proprio, he has closed the administrative path that could have led to divorce.

"Those who think this is 'Catholic divorce' are wrong because this last document has closed the door to divorce by which it could have entered. It would have been easier with the administrative path," he said.

"This document, this 'motu proprio,' facilitates the processes and the timing, but it is not divorce because marriage is indissoluble when it is a sacrament. And this the Church cannot change. It's doctrine. It's an indissoluble sacrament."

On Sept. 8 Pope Francis made significant changes to the marriage nullification process, giving more of a role to local bishops, dropping the automatic appeals, and declaring the process free of charge.

The changes were published in two motu proprio - or letters issued by the Pope "on his own initiative." The documents were entitled "Mitis Iudex Dominus Iesus" (The Lord Jesus, a meek judge), which deals with modifications in the Latin Rite's Code of Canon Law, and "Mitis et misericors Iesus" (Jesus, meek and merciful), which outlines changes for Eastern Churches who, although in full communion with Rome, have historically had a different process.

Francis noted that the streamlined process was asked for by last year's synod participants, since there are some cases that take up to 10-15 years.

"There's one sentence, then another sentence and after there's an appeal, there's the appeal then another appeal. It never ends," he said.

Although Pope Benedict XIV instituted the double-sentence in his time, it was because there were "some abuses" being made in the process in central Europe, the Pope noted, and that to stop it "he introduced this but it's not something essential to the process."

"The procedure changes, jurisprudence changes, it gets better," he said, noting that although at the time it was an urgent need, times change and even Pius X wanted to streamline the annulment process but didn't "have time or the possibility to do it."

On the topic of the coming synod, Pope Francis said that the issues surrounding divorced persons who enter into new marriages will be discussed, as can be seen in the "instrumentum laboris," or working document, for the discussion.

However, he also stressed that there are many others issues to be addressed besides just new unions and communion for the divorced and remarried, such as the growing number of youth who don't want to marry, personal maturity when entering into the sacrament and faith.

Marriage preparation is also an important point to address, he said, adding that "I think so often that to become a priest there's a preparation for eight years, and then, it's not definite, the Church can take the clerical state away from you."

"But, for something lifelong, they do four courses! Four times... Something isn't right. It's something the synod has to deal with: how to do preparation for marriage. It's one of the most difficult things."

He said that the many problems needing attention can be found in the synod's "Instrumentum laboris," but said he was glad to get a question on "Catholic divorce," and clarified that "it doesn't exist."

"Either it wasn't a marriage, and this is nullity - it didn't exist. And if it did, it's indissoluble. This is clear."

Published June 23, the "Instrumentum Laboris," has been compiled by the Vatican department in charge of organizing the synod to guide this October's discussions.

Divided into three parts, it builds on the final report of last October's synod, also incorporating suggestions from Church entities like bishops' conferences and even individuals who freely sent their opinions.

The final instrumentum was reviewed by the Congregation for the Doctrine of the Faith before its publication, according to a source familiar with the document.

Set to take place Oct. 4-25, this year's ordinary synod will reflect on the theme "Jesus Christ reveals the mystery and vocation of the family" will gather more than 200 Bishops and representatives from all over the world. The conclusions of the gathering will be used by Pope Francis to draft his first Post-Synodal Exhortation, which can be expected in 2016.

In the document it is noted that various opinions have been expressed by synod fathers on the topic of communion for the divorced and remarried, including suggestions to keep the current practice.

Others have asked that each individual case be examined, and that couples in special circumstances be allowed to receive the Eucharist after completing a journey of penance and reconciliation guided by the local bishop.

The document emphasizes that the question is still being discussed, and that particular emphasis should be given to the distinction between "objective situations of sin and extenuating circumstances."